Page 1 PROGRESS REPORT THE SOLAR-A SOFT X-RAY TELESCOPE (SXT) PROGRAM (CONTRACT NAS8-37334) (for April 1994) OVERVIEW 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 from Kagoshima Space Center (KSC) in Japan, and renamed Yohkoh. The purpose of this mission is to study high energy phenomena in solar flares. 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 by Lockheed 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 primary activity besides performing the usual managerial tasks relate to the extended mission. Planning is continuing as to the scientific emphasis and the resource allocation. There will also be a new SXT poster unveiled at the AGU meeting later this month. << Solar Activity >> Solar activity declined this month to the lowest levels since 1988. Only six small (GOES C-class) flares were observed. The minimum level of solar X-ray output was between 5 and 13 April when it shrunk to about 1% of the typical background level at solar maximum. This corresponded to the time when a large area of coronal hole was pointed towards the Earth and no active regions were visible on the solar disk. This resulted in the Earth being bathed in the high-speed solar wind (>700 km/s) for several days and caused dangerous electrical charging on geosynchronous satellites. Just because activity drops it does not mean that the Sun does not continue to do interesting things, Yohkoh observed a huge eruption near the south pole on 14 April starting at about 02:00 UT. It stretched for over a million kilometers across the solar disk and continued to expand for over a day. There was probably no signature of this event at optical wavelengths as it did not seem to be associated with a filament eruption or an active region flare. However Yohkoh data was instrumental in forecasting the terrestial effects of Page 2 this event, as can be seen from the following extract from an SEL report (somewhat paraphrased to be more concise): "Five electric power transformers in the Chicago area have failed in the past few weeks, probably due to induced currents associated with episodes of elevated geomagnetic activity. The transformers are worth $5M to $10M each, and it is estimated that up to $0.5M per day in revenues may be lost until the transformers are be replaced. Due to the great expense of operating without the necessary transformers, Commonwealth Edison planned to put a replacement transformer into service at the Zion Power Station on April 16. As this date approached, the Sun, as imaged by the Japanese satellite Yohkoh, ejected a large massive structure. Such structures are frequently associated with geomagnetic disturbances. Based on these observations, forecasters at the Space Environment Services Center raised their probabilities for geomagnetic storm conditions to 55% for April 16 and 17. Commonwealth Edison decided that the risk to the transformer justified the cost of postponing the transformer installation until the disturbance was predicted to subside. The storm began on April 16, and attained "severe storm" level and aurora were seen as far south as Boulder, Colorado. By Sunday the storm had declined and the new transformer was successfully installed." << Campaigns >> Yohkoh supported the launch of the Solar Plasma Diagnostics Experiment (SPDE) rocket at 20:45 UT on 25 April. The launch was perfect, and the attitude control system performed well. Processing of the flight films has been completed and there are usable images from every instrument system. SPDE obtained EUV images which will provide excellent plasma temperature diagnostics with SXT filtergrams. The TRC (UV) images show intricate loops all round the solar limb and may have caught a subflare. SXT will provide excellent context information on the evolution of the solar features that SPDE observed and obtained detailed narrow-band imaging and spectra. SXT also ran a successful X-ray Bright Point campaign at the end of April supported by KPNO and Mees Observatory. Page 3 << Science >> Much of our effort this month has gone into preparing for the AGU/AAS-SPD meeting in Baltimore, MD in May. Several of the SXT team are involved in arranging the programme for this meeting, giving invited talks, chairing sessions, and preparing posters. We have been especially busy helping prepare posters and presentations with several of the Ulysses and Spartan groups. There has been a significant amount of publication activity over the last month or so: - Papers Published (17) - "Morphology of Active Region Transient Brightenings with the YOHKOH Soft X-ray Telescope", T. Shimizu, S. Tsuneta, L. Acton, J. Lemen, Y. Ogawara, and Y. Uchida, ApJ, 422, 906-911, 1994. "Multispectral Observations of Chromospheric Evaporation in the 1991 November 15 X-Class Solar Flare", J.-P. Wuelser, R.C. Canfield, L.W. Acton, J. L. Culhane, A. Phillips, A. Fludra, T. Sakao, S. Masuda, T. Kosugi, S. Tsuneta, Astrophys. J., 424, 459 (1994). "Patterns of Helicity in Solar Active Regions", A. A. Pevtsov, R. C. Canfield, and T. R. Metcalf, ApJ, 425, L117, 1994. "Diagnostics of Twisted Flux Emergence (NOAA AR7260)", K.D. Leka et al., in "X-ray Solar Physics from Yohkoh", eds. Y. Uchida, T. Watanabe, K. Shibata, and H. Hudson, 1993, p. 25. "Two types of interaction between emerging flux and coronal magnetic field", K. Shibata, N. Nitta, R. Matsumoto, T. Tajima, T. Yokoyama, T. Hirayama, and H. Hudson, in "X-ray Solar Physics from Yohkoh", eds. Y. Uchida, T. Watanabe, K. Shibata, and H. Hudson, 1993, p. 29. "Yohkoh observations of weak events within AR 7218", G. A. Linford, H. Hudson, and A. S. Sterling, in "X-ray Solar Physics from Yohkoh", eds. Y. Uchida, T. Watanabe, K. Shibata, and H. Hudson, 1993, p. 49. "Electric currents and coronal structures in NOAA active region 6952", T. R. Metcalf, R. C. Canfield, H. S. Hudson, D. L. Mickey, J.-P. Wuelser, and S. Tsuneta, in "X-ray Solar Physics from Yohkoh", eds. Y. Uchida, T. Watanabe, K. Shibata, and H. Hudson, 1993, p. 55. Page 4 "Evidence for impulsive soft X-ray bursts during flares," K. Strong, H. Hudson, and B. Dennis, in "X-ray Solar Physics from Yohkoh", eds. Y. Uchida, T. Watanabe, K. Shibata, and H. Hudson, 1993, p. 65. "H-alpha and X-Ray signatures of chromospheric evaporation observed during the early phase of the 15 November 1991 flare", J.-P. Wuelser, R. C. Canfield, L.W. Acton, J. L. Culhane, A. Phillips, A. Fludra, T. Sakao, S. Masuda, and T. Kosugi, in "X-ray Solar Physics from Yohkoh", eds. Y. Uchida, T. Watanabe, K. Shibata, and H. Hudson, 1993, p. 75. "Flares in active region NOAA 7260", N. Nitta, L. van Driel-Gesztelyi, K. D. Leka, T. Sakurai, K. Shibata, K. Ichimoto, R. C. Canfield, J.-P. Wuelser, T. R. Metcalf, and D. L. Mickey, in "X-ray Solar Physics from Yohkoh," eds. Y. Uchida, T. Watanabe, K. Shibata, and H. Hudson, 1993, p. 111. "Morphological evolution of the post-flare loops of June 25-26, 1992" B. Anwar, E. Hiei, H. S. Hudson, L. W. Acton, T. Metcalf, and J. Lemen, in "X-ray Solar Physics from Yohkoh," eds. Y. Uchida, T. Watanabe, K. Shibata, and H. Hudson, 1993, p. 121. "Non-thermal effects in slow solar flares", H. S. Hudson, L. W. Acton, A. C. Sterling, S. Tsuneta, J. Fishman, C. Meegan, W. Paciesas, and R. Wilson, in "X-ray Solar Physics from Yohkoh," eds. Y. Uchida, T. Watanabe, K. Shibata, and H. Hudson, 1993, p. 143. "The X flare of 15 November 1991: preflare flux emergence, heating, and filament eruption", R. C. Canfield, K. A. Blais, A. N. McClymont, T. R. Metcalf, K. P. Reardon, J.-P. Wuelser, L. W. Acton, H. Kurokawa, and T. Hirayama, in "X-ray Solar Physics from Yohkoh," eds. Y. Uchida, T. Watanabe, K. Shibata, and H. Hudson, 1993, p. 153. "Coronal eruptions observed by Yohkoh", J. A. Klimchuk, L. W. Acton, K. L. Harvey, H. S. Hudson, K. L. Kluge, D. G. Sime, K. T. Strong, and Ta. Watanabe, in "X-ray Solar Physics from Yohkoh," eds. Y. Uchida, T. Watanabe, K. Shibata, and H. Hudson, 1993, XRSPY, p. 181. "Interplanetary consequences of transient coronal events", Ta. Watanabe, M. Kojima, Y. Kozuka, S. Tsuneta, J. R. Lemen, H. Hudson, J. A. Joselyn, and J. A. Klimchuk, in "X-ray Solar Physics from Yohkoh," eds. Y. Uchida, T. Watanabe, K. Shibata, and H. Hudson, 1993, p. 207. "A loop-loop interaction observed with Yohkoh SXT", M. Page 5 Akioka, L. W. Acton, and H. S. Hudson, in "X-ray Solar Physics from Yohkoh," eds. Y. Uchida, T. Watanabe, K. Shibata, and H. Hudson, 1993, p. 241. - Books published (1) - "X-ray Solar Physics from Yohkoh", eds. Y. Uchida, T. Watanabe, K. Shibata, and H. Hudson (Universal Academy Press, Tokyo) 1993. - Papers accepted (3) - "Electric Currents and Coronal Heating in NOAA Active Region 6952", T. R. Metcalf, R. C. Canfield, H. S. Hudson, D. L. Mickey, J.-P. Wuelser, P. C. H. Martens, and S. Tsuneta, Astrophys. J., June 1994. "A Gigantic X-ray Jet Observed by Yohkoh", K. Shibata, H. S. Hudson, et al., Ap. J. (Lett.) "Analysis of three Yohkoh white-light flares", H.S. Hudson, L. van Driel-Gesztelyi, and T. Kosugi, proc. Kofu Symposium - Papers submitted (4) - "Detection of 17 GHz Radio Emission from X-ray Bright Points", M. R. Kundu, S. Enome, K. Shibasaki, N. Nitta, ApJ Letters "Is the Solar Chromospheric Magnetic Field Force-Free?", Thomas R. Metcalf, Litao Jiao, Han Uitenbroek, Alexander N. McClymont, and Richard C. Canfield, Astrophys. J. "Resolving the 180 Degree Ambiguity in Vector Magnetic Field Measurements: The 'Minimum' Energy Solution", Thomas R. Metcalf, Solar Phys. "Particle Acceleration and the Decay of Soft X-ray Non-thermal Line Broadening" D. Alexander and S. Mathews, Solar Phys. - Presentations (3) - "Soft X-Ray Loops and the Heating of the Solar Corona," J. A. Klimchuk, Univ. of California at Berkeley, 8-April-94 (invited). "Coronal Magnetic Field Reconstruction: A New Window on the Corona," G. Roumeliotis, Space Science Lab, Berkeley, 26-April-94 (invited). Page 6 "Soft X-Ray Loops and Coronal Heating," J. A. Klimchuk, ISAS, Japan, 28-April-94 (invited). - Abstracts (3) - "Flare Activity and Active Region Evolution as Observed by Yohkoh/SXT", N. Nitta, L. v. Driel-Gesztelyi, K. D. Leka, (K. Shibata), COSPAR "Flare Activity and Active Region Evolution as Observed by Yohkoh/SXT", N. Nitta, L. v. Driel-Gesztelyi, K. D. Leka, (K. Shibata), SPD/AGU "X-Ray Bright Points: The Signature of Magnetic Field Reconnection", Karen L Harvey, Frances Tang, Hal Zirin, Sara Martin, Hugh Hudson, Don Mickey, Marilyn Bruner, James Lemen, Keith Strong, Nariaki Nitta, Saku Tsuneta, AGU/SPD meeting, May 1994 << Public Use of SXT Images >> Another article was published in Sky & Telescope covering X-ray activity on the Sun this month by Gary Linford and Keith Strong. The AGU has confirmed the invitation for Keith Strong to give a public lecture at the Maryland Science Center during the AGU on the "The Violent Sun". He has also been invited to give a public lecture at the Technical Museum of Innovation in San Jose as part of the Lockheed Corporate Recognition Month.. A great deal of work, primarily by Gary Linford, has gone into the production of a new Yohkoh poster. This features an extended X-ray image of the Sun taken by offsetting SXT to the east and west limbs and mosaicing the resulting images together. This poster will emphasize educational outreach. It has a series of panels printed on the back showing how to observe eclipses with a pinhole camera, make a sundial, and a description of the different layers of the solar atmosphere. We continue to distribute the "Our Star The Sun" poster and Yohkoh PR videos around the world. Page 7 << Data Flow >> ------------------------------------------------------------------------------ Month Full Frame Images Observing Region Images Received Lost Received Lost Loss % QT FL Tot ------------------------------------------------------------------------------ Sep-91 517 397 21174 3541 24715 5481 18.15 Oct-91 4106 2532 6393 12437 18830 3401 15.30 Nov-91 5291 2475 12149 14696 26845 10952 28.98 Dec-91 4896 3190 5001 16837 21838 6892 23.99 Jan-92 5544 3177 10084 5972 16056 6849 29.90 Feb-92 5305 2803 16932 11382 28314 12019 29.80 Mar-92 6248 2361 20367 2653 23020 9458 29.12 Apr-92 6734 3500 20094 5423 25517 12390 32.69 May-92 7032 3158 25464 4589 30053 13745 31.38 Jun-92 7230 2819 24375 13361 37736 11419 23.23 Jul-92 6535 3085 24622 11481 36103 13065 26.57 Aug-92 6572 2978 24207 11154 35361 13550 27.70 Sep-92 6087 2916 26832 20042 46874 15729 25.12 Oct-92 6743 2589 50985 14709 65694 23687 26.50 Nov-92 6658 2939 24416 14696 39112 12924 24.84 Dec-92 6747 3027 24147 6600 30747 12495 28.90 Jan-93 6888 3351 24067 4861 28928 13069 31.12 Feb-93 6833 3004 24479 18149 42628 12302 22.40 Mar-93 7177 3460 25874 19537 45411 14657 24.40 Apr-93 7754 3644 34128 8352 42480 17967 29.72 May-93 8571 3950 41832 7518 49350 21971 30.81 Jun-93 7340 2589 64545 12539 77084 26299 25.44 Jul-93 8259 3650 47561 5352 52913 24213 31.39 Aug-93 7628 3638 30705 3563 34268 17436 33.72 Sep-93 6875 2899 22697 5600 28297 11252 28.45 Oct-93 7474 3657 33782 7548 41330 20104 32.72 Nov-93 8504 3864 42953 5849 48802 23896 32.87 Dec-93 5898 3047 21128 13297 34425 13001 27.41 Jan-94 6934 2804 28567 10960 39527 13746 25.80 Feb-94 6948 2892 22815 5819 28634 11463 28.59 Mar-94 7736 2627 69273 3733 73006 31464 30.12 Apr-94 4660 1977 15914 3390 19304 8456 30.46 ------------------------------------------------------------------------------ Total 207724 94999 887562 305640 1193202 465352 28.06 ------------------------------------------------------------------------------ Number of Full Frame Images Received: 207724 Number of Observing Region Images Received: 1193202 Total: 1400926 Approximate Number of Shutter Moves/CCD Readouts: 2446776 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 8 << 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 (%) -------------------------------------------------------------------------------- Oct-91 31.07 21.3 509 261 10.5 77.8 Nov-91 31.06 20.9 648 277 11.9 64.4 Dec-91 31.04 20.2 804 353 14.0 52.5 Jan-92 31.13 23.6 985 450 0.5 / 2 14.9 38.4 Feb-92 31.32 30.8 1176 544 14.3 31.7 Mar-92 31.47 36.5 1355 626 14.8 25.1 Apr-92 31.44 35.2 1323 610 23.8 / 4 14.6 22.8 May-92 31.65 43.1 1417 653 14.4 20.1 Jun-92 32.12 60.9 2215 880 -2.5 / 3 15.1 17.4 Jul-92 32.19 63.2 1829 822 15.5 14.1 Aug-92 32.21 64.1 1922 886 14.9 13.1 Sep-92 32.38 70.5 2062 954 -1.2 / 3 15.9 12.2 Oct-92 32.64 80.3 2317 1055 16.8 11.5 Nov-92 36.24 215.1 6112 1391 18.0 11.0 Dec-92 42.58 452.8 17390 2024 17.9 N/A Jan-93 42.59 453.1 13006 2034 23.8 / 2 19.2 N/A Feb-93 42.28 441.5 13895 2090 17.7 N/A Mar-93 43.14 473.8 14047 2151 17.7 N/A Apr-93 43.13 473.4 14304 2146 23.8 / 2 16.9 N/A May-93 43.45 485.3 16405 2357 17.3 N/A Jun-93 44.03 507.2 20037 2531 16.3 N/A Jul-93 44.52 525.6 23977 2700 22.5 / 2 17.7 N/A Aug-93 44.24 515.0 21879 2643 25.2 / 3 17.2 N/A Sep-93 45.07 546.2 27469 2745 17.5 N/A Oct-93 45.40 558.6 31684 2982 17.7 N/A Nov-93 45.33 555.8 32047 3210 23.8 / 3 19.7 N/A Dec-93 45.92 578.1 38515 3101 19.2 N/A Jan-94 46.18 587.9 42560 3464 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 46.03 582.1 42416 3837 25.2 / 3 17.9 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 9 << Personnel Travel >> - SXT travel for the month of April 1994 - SXT Foreign Travel between 1-APR-94 and 30-APR-94 List was Generated: 5-May-1994 16:02:25.00 PR_TRAV_SUMM Ver 1.0 29-Apr-92 ACTON 1-APR-94 * 30-APR-94 * 30 (total of 30 days) ALEXANDER 2-APR-94 30-APR-94 * 29 (total of 29 days) HUDSON 1-APR-94 * 30-APR-94 * 30 (total of 30 days) SLATER 1-APR-94 * 21-APR-94 21 (total of 21 days) LABONTE 1-APR-94 * 30-APR-94 * 30 (total of 30 days) HARVEY 1-APR-94 * 11-APR-94 11 (total of 11 days) KLIMCHUK 21-APR-94 30-APR-94 * 10 (total of 10 days) ---------------------------------------------------------------- Grand Total of 161 days for 7 people NOTE: The "*" signifies travel that actually ends after 30-APR-94 - Planned SXT travel for the month of May 1994 - SXT Foreign Travel between 1-MAY-94 and 31-MAY-94 List was Generated: 5-May-1994 16:03:35.00 PR_TRAV_SUMM Ver 1.0 29-Apr-92 ACTON 1-MAY-94 * 1-MAY-94 1 (total of 1 days) ALEXANDER 1-MAY-94 * 31-MAY-94 * 31 (total of 31 days) BRUNER 2-MAY-94 20-MAY-94 19 29-MAY-94 31-MAY-94 * 3 (total of 22 days) HUDSON 1-MAY-94 * 16-MAY-94 16 30-MAY-94 31-MAY-94 * 2 (total of 18 days) SLATER 1-MAY-94 31-MAY-94 * 31 (total of 31 days) LABONTE 1-MAY-94 * 31-MAY-94 * 31 (total of 31 days) KLIMCHUK 1-MAY-94 * 3-MAY-94 3 (total of 3 days) ---------------------------------------------------------------- Grand Total of 137 days for 7 people NOTE: The "*" signifies travel that actually ends after 31-MAY-94 Respectfully submitted, Keith T. Strong Frank Friedlaender Page 10 MONTANA STATE UNIVERSITY (LOREN ACTON) During the reporting period the center of mass of the MSU team shifted to Japan. Acton served there as SXT Chief Observer for both March and April and Alexander joined him for the month of April, trained as Chief Observer, and remains at ISAS in this capacity for May. During March Alexander submitted a paper entitled "Particle Acceleration and the Decay of Soft X-ray Non-thermal Line Broadening" to Solar Physics with co-author Sarah Matthews of the University of Glasgow. He also completed teaching a special projects course at MSU in Solar Astrophysics and received approval to offer a listed graduate level course, Phys 515 - The Physics of Astrophysics, in spring semester 1995. In addition to course work and serving as MSU/SXT computer systems manager Brian Handy is preparing a poster paper entitled "Creation and Heating of Inter-Region Coronal Loops" with Acton, Alexander, Metcalf, Hudson and Shimizu for the AGU/SPD meeting in Baltimore. This paper examines the loop system connecting AR7260 to AR7264 to the east in order to quantify the brightening of these long (20 degress in longitude) loops in connection with the increase in activity in AR7260. Acton is preparing 2 papers for the AGU/SPD meeting. The first, an invited talk entitled "X-ray Studies of the Solar Corona by Yohkoh" will discuss eruptive events. He will concentrate primarily on two events in this illustrative talk. (1) The 14-April-94 south polar eruption with great geophysical effects (movie prepared by Greg Slater), and (2) observational evidence for magnetic reconnection in the 22-April-92 eruptive flare with Akioka and Hudson. He has also prepared a contributed paper entitled "Radiative Energy Losses of the Solar Corona" with Hara and Morrison that examines the evolution of coronal x-ray brightness since the start of routine SXT observing in early November 1991. We are delighted to report that an MSU PhD student, Mark Weber, has been awarded a fellowship for graduate studies by the Montana Space Grant Consortium and has chosen to begin his thesis research this coming summer with the Solar Group using SXT data. Page 11 SOLAR PHYSICS RESEARCH CORPORATION (KAREN L. HARVEY) Activity the last two months are as follows: (1) Traveled and worked at ISAS in Japan from March 21 to April 11. This work concentrated on the reduction and processing of the SXT PFIs obtained primarily during the latest XBP collaboration in March 1994. The processing scheme was then applied to the SXT data from previous XBP runs. (2) continuation of the multi-observatory collaborative observing program to study X-ray bright points. The latest observing campaign took place 27 April to 1 May 1994 and involved the Yohkoh SXT, NSO/KP, BBSO, and MSO. The objective of this run was to study variations and the association of He I 10830 dark points and X-ray bright points. (3) continuation of a study of evolution of the magnetic field structures underlying X-ray jets in collaboration with K. Shibata. Discussions were held with Shibata during my visit to Japan on this study. It was decided to determine the types of change occurring in the magnetic structures associated with events being studied by Mr. Shimojo during 1 November 1991 to 30 April 1992. An additional study of the magnetic field changes and X-ray jets will involve just a few well observed events. Two papers at this stage are planned. (4) began assessing SXT images during selected intervals during 1993 for XBP counts within a lobe of the polar coronal hole at the South Pole in collaboration with G. Poletto and S. Suess. The study objective is to determine if XBPs (used as a `proxy' for polar plumes) occur in sufficient numbers to account for the mass flux in coronal holes. (5) continued updating of bibliography of Yohkoh papers; the bibliography is being restructured for easier access as per conversations with N. Nitta and K. Strong. A list of papers in refereed journals and meeting proceedings separated by year was compiled, and is now available on the Lockheed and ISAS computers. (6) contacted by the producers of `Disney Presents Bill Nye the Science Guy' for an interview on solar astronomy. They were interested in showing some Yohkoh SXT sequences in addition to a tour of the National Solar Observatory telescopes and facilities at Kitt Peak. Page 12 STANFORD UNIVERSITY (DR. P. STURROCK) During this period, Jim Klimchuk and Lisa Porter continued their study of coronal loops. A significant discovery, of relevance to many Yohkoh investigations, is that the SXT measurements of temperature and emission measure are not normally distributed. That is, a measurement of temperature or emission measure is a sample from a distribution of possible measurements that is not Gaussian. For certain cases, especially cases of low count rates, the distribution can be highly non-Gaussian, with substantial power in the wings of the distribution. The standard deviations of these distributions suggest that the temperature and emission measure uncertainties output by analysis programs like sxt_teem.pro may significantly underestimate the true uncertainties. We caution that these conclusions are preliminary and that further investigation of these effects is necessary. Because the temperature, emission measure, and pressure measurements are not normally distributed, it is advisable to use non-standard statistical methods when studying correlations among different loop parameters (e.g., pressure and length or temperature and length). We have therefore developed IDL procedures to perform nonparametric, or ranked-ordered, statistical analyses. With these analyses, we find that pressure varies inversely with loop length and that temperature is uncorrelated with loop length. Both results imply that the heating rate averaged along the loop varies inversely with the square of the loop length. This is an important constraint on coronal heating theories. We have developed one simple theory which seems to explain the observations. Much of the work on non-normal distributions and nonparametric statics was performed while Klimchuk was visiting ISAS between April 20 and May 3. Also during this period, George Roumeliotis continued to develop his code for computing extrapolations of photospheric magnetic field measurements (coronal magnetic field reconstruction). He has been grappling with the issue of the 180-degree ambiguity in the measurements and has been testing his code against "known" solutions (solutions generated by Klimchuk's 3-D force-free field code that uses footpoint positions rather than vector field components as boundary conditions). Over the next two months, we will continue the work described above. Page 13 UNIVERSITY OF CALIFORNIA AT BERKELEY (DR. S. KANE) J. McTiernan has been working combination BCS-HXT analysis of flares, for a large sample of events, in order to calculate the low energy cutoff of nonthermal emission. Preliminary results were presented at a seminar at Lockheed on May 3, and improved results will be presented at the May '94 SPD meeting in Baltimore. Contrary to what was found in the initial analysis, the results show that the low energy cutoff has a lower limit of approximately 20 keV. We have also started work on adapting a maximum likelihood method for deconvolution of SXT images using the SXT point spread function, since using the Maximum Entropy Method has so far been not very successful. Work is continuing on multispacecraft observations of hard X-rays using Yohkoh, Ulysses and BATSE results, and Sharad Kane will present a paper based on these comparisons at the SPD meeting, and the COSPAR meeting in Hamburg in July. Page 14 UNIVERSITY OF HAWAII ACTIVITY REPORT (DR. R. CANFIELD) << Major Activities For The Months Of March And April >> Our most important activities included support of Yohkoh operations and data analysis at ISAS, coordinated ground-based data acquisition at Mees (including two campaigns), development of full-disk observing capabilities, analysis of Yohkoh/Mees data, organization of meetings, participation in meetings, and preparation of manuscripts. A topic was selected for the next Hawaii CDAW: Coordinated Observations of Eruptive Events. K. Shibata agreed to be the J-side organizer, and R. Canfield will handle US arrangements. It is expected that the CDAW will be held in October or November. Operational support for SXT was provided by Hudson, Jiao, and LaBonte at ISAS (SSOC Toban), Judd, Nitta, and Douglass at Mees (observatory operations), and Canfield, Jiao, Leka, Metcalf, and Wuelser in Manoa (Mees Yohkoh Duty Scientist). Mees carried out coordinated observations during the X-ray Bright Point Campaign at the end of April. While the Mees observations were compromised by intermittent clouds at the start of the campaign, good data were obtained, particularly on the final day. Mees data consist primarily of vector magnetograms and H-alpha imaging spectra, but also include H-alpha coronagraph video, full-disk Ca K-line images, and full-disk white light images. Mees also supported the Solar Plasma Diagnostics Experiment (SPDE), lead by Bruner. Mees had favorable observing conditions before and during the rocket launch, while some of the solar observatories on the mainland reported clouds. The Mees observations include vector magnetograms of the more important active regions shortly before the rocket launch, rapid sequences of vector magnetograms and H-alpha imaging spectra of the SPDE target during the rocket flight, and full sun vector magnetograms within 24 hours before and after the launch. The level of travel activity was modest. Jiao spent four weeks at ISAS, doing research for his thesis and toban duty. Hudson and Canfield attended the MSV working group meeting in Huntsville at the end of April, which was devoted to discussion of the next Japanese solar mission. Metcalf submitted his paper with Jiao studying the height dependence of the magnetic field in AR7216. The field is not force-free at the photosphere but becomes force-free Page 15 about 400 km above the photosphere. He implemented a new idea for the resolution of the 180 degree ambiguity in vector magnetograph data involving the approximate minimization of the energy in the field. The technique works very well is physically well founded. He continued his analysis of the IVM H-alpha data from October, 1992. In particular, he investigated methods for reducing the errors due to differential blurring of the raw IVM images. He worked with Roumeliotis on vector magnetic field data from AR6952 and AR6982 with the eventual goal of extrapolating the field into the corona with a non-linear force-free extrapolation. Leka worked on a manuscript on the evidence for twisted emerging flux in AR 7260, but decided to hold it in abeyance until completion of the quantitative analysis of current and magnetic flux emergence, to be presented at the SPD meeting. Hudson completed the work on Yohkoh/SXT white-light flares with mm-wave gradual components for publication in the Kofu conference proceedings. He also helped with the paper by Shibata et al. on X-ray jets, which was accepted by Ap. J. for publication. Other scientific work mainly included development effort on coronal phenomena, including model calculations to support investigations of off-the-limb and coronal hole observations by SXT. The quiet conditions made it possible for Acton to obtain deep exposures of a "clean" coronal hole off the S limb in February, via offpointing, and he and Culhane confirmed the earlier result of Lemen that the SXT coronal emission extends much further out than had been expected. This is technically a nice result because it shows that the stray light does not materially interfere with faint photometry, a result confirmed by studies of the data from the eclipse of Nov. 13, 1993. Hudson has qualitatively explained the slow falloff of coronal brightness based upon the models, but there is still a problem with the SXT "color temperature". Hudson also worked on the polar crown filament events of 24 Feb. 1993 and 14 Apr. 1994, developing software for analysis of the SXT composite images. This work is part of the material included in a riposte to Gosling's misleading paper in JGR entitled "The Solar Flare Myth". Wuelser mostly finished the data analysis part of his study of several large flares. The study is based on a combination of Mees imaging spectroscopy and Yohkoh X-ray data, and attempts to establish the quantitative relationship between chromospheric heating, chromospheric evaporation, and chromospheric and coronal flare energetics. Page 16 The upgrade of the Mees CCD imaging spectrograph (MCCD) is in the final shakeout phase. Wuelser obtained a first full sun mosaic with this new setup and wrote the necessary software to analyze the new type of data. The new setup was also used during the X-ray Bright Point campaign between April 27 - May 1. Wuelser completed and tested the software to co-align ground-based and Yohkoh data through images from the Mees White Light Telescope (MWLT). The results show that the MWLT meets its design goal with an absolute co-alignment accuracy better than 2 arcseconds. Jiao, with Canfield and Klimchuk, wound up his analysis of three diverse active regions, looking for relationships between the shape of SXT loops and the density of vertical electrical currents at their footpoints. He found that all three regions show a significant inverse correlation between loop thickness asymmetry and footpoint Jz asymmetry. These findings support the hypothesis that the coronal flux tubes studied are force-free. Canfield and Reardon continued their study of approximately eight X-ray jets and H-alpha surges in AR 7260. Reardon co-registered the MCCD H-alpha and X-ray data and produced clean filtered H-alpha filtergrams. Reardon's most interesting discovery is strong downflows beneath the apparent reconnection point, as well as upflows (jets) above it. << Plans For May And June >> Metcalf plans to continue the analysis of the IVM H-alpha polarization data in preparation for the AGU/SPD meeting. He will continue to work with Roumeliotis on the extrapolation of photospheric magnetic fields into the corona. He will spend the month of June visiting ISAS and plans to work with Hudson and Kosugi applying the Pina and Puetter deconvolution algorithm to HXT data. Leka plans to work on the quantitative analysis of emerging flux and currents in AR 7260 and to present the results at the AGU/SPD meeting. Hudson's main focus will remain on the Ulysses/Yohkoh comparisons. There are several meetings at which this will be of interest: the AGU/SPD meeting, at which time he would like to coordinate with McAllister and others on the remarkable event of 14 April 1994, the IACG workshop in Tokyo at the beginning of June, and the STEP meeting in Nakaminato in the middle of June. In addition he intends to submit the comment on Gosling's paper and a paper in Page 17 presentation on the early stages of the 21 Feb. 1992 event (the subject of a contributed paper at the SPD/AGU meeting). Wuelser plans to present the results of his chromospheric heating and flare energetics study at the AGU/SPD meeting. In June he will focus his efforts on the analysis of the August 20, 1992 flare with Bastian. This flare was exceptionally well observed by Mees, Yohkoh and the VLA. Jiao will present his work on loop cross-sections and currents at the AGU/SPD meeting. He plans to complete his thesis proposal on the theoretical modeling of coronal fields based on Mees vector magnetograms and comparison of the results with SXT data. Reardon will present the work on X-ray jets and surges at the AGU/SPD meeting. After the meeting, he and Canfield will begin writing up the results. Page 18 -------------------------------------------------------------------------------- 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 May 1994 April 1994 |-------------------------------- | 6. PERFORMING ORGANIZATION | CODE: O/91-30 -----------------------------------------------|-------------------------------- 7. AUTHOR(S) | 8. PERFORMING ORGANIZA- K. T. Strong | 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 - 37334 -----------------------------------------------|-------------------------------- 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 April 1994 |-------------------------------- |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, Washington, D.C. 20402-0001