Page 1 PROGRESS REPORT THE SOLAR-A SOFT X-RAY TELESCOPE (SXT) PROGRAM (CONTRACT NAS8-37334) (for April 1995) 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 NASA-purchased computers are now operational in Japan. These workstations are several times more capable than the original computers that were installed at the time of the YOHKOH launch in August 1991. These computers are used to reformat the entire mission data set. Previously, a week's worth of data took three or four days to reformat. The new Alpha OSF workstations complete this task in only about 12 hours. These computers are also used by LSAL and Co-I scientists visiting Japan, and they are a significant improvement for the scientific analysis and research activities. An offer was made for our post-doc position, but it was not accepted by the candidate. Other potential candidates are being evaluated. << Solar Activity >> The Sun continues to be relatively two-faced. That is, during the past month there were about two weeks of low activity and two weeks of activity from essentially one active region. The month began with a fairly low level of X-ray flux. During the middle of the month AR 7863 appeared at the east limb and began to grow. This region and AR 7864 produced more than a dozen C class flares, several M flares, and three X flares. As these two regions rotated over the west limb, the GOES level dropped over five decades to A-level and it occasionally seemed to drop out all together, perhaps marking the lowest X-ray activity level since the launch. Consistent with this is that after Ar7863/7864 rotated over the west limb it was no longer possible to discern a S XV spectrum, even Page 2 with relatively long integrations (200s). Normally, S XV spectra are obtained with fairly short integrations. In early May, a new region appeared at the east limb to continue the low-high-low-high solar activity pattern. << Campaigns >> The campaign to acquire a good set of terminator images as a function of spacecraft pointing and SXT filter was continued last month. During March it was realized the the terminator operations can thwart the efforts of the KSC tohbans to recover the SXT from an SEU under certain circumstances. Samuel Freeland and Hirohisa Hara modified the SXT recovery procedure to remedy this situation. The NRL HRTS rocket was flown from White Sands on 18-Apr-95. The SXT partial frame field of view was set fixed to the same active region target as the rocket by operating the SXT in ARS2 pointing mode. John Cook of NRL reports that the film has been recovered from the rocket payload and has been developed. We look forward to comparing results of the SXT images with the UV images and from other participating ground- based observatories. An attempt was made to accomplish a bright-point observing campaign, organized by Karen Harvey. However, as it turned out, the time of the campaign coincided with the time of greatest solar activity for the month, so this campaign was not carried out. It will be attempted again in mid-June. N. Gopalswamy (University of Maryland) observed at the VLA on 12, 15, 16 April. His observing target was AR 7863, which was also the Yohkoh and Mees targets. At the end of the month there was an attempt to observe a filament eruption in soft X-rays with higher time resolution and possibly higher spatial resolution. No eruption was observed this time, but the procedure for coordinating this type of campaign with Mees, Yohkoh, Big Bear and the Soon Sites (through Alan Kiplinger) now works well. We will continue to attempt this campaign again when the conditions permit. Future plans include campaigns to observe filaments and XBPs as well as to support SERTS, SPARTAN, and Ulysses' passage over the northern pole of the Sun in the coming months. << Science >> Preparations are proceeding for the IAU symposium to be held at Makuhari, near Tokyo in May. Several of us are preparing talks for the American Geophysical Union meeting's special session on the "Flare Myth" and for the Solar Physics Division Meeting in Memphis. In addition, preparations are being made for the IAU colloquium in Nagoya and the SolWind 8 meeting at Dana Point in June. Page 3 << Publications>> The following is an incomplete listing of work in progress on papers and presentations that include scientists that are supported by the NASA SXT contract. Karen Harvey maintains a bibliography of refereed and conference papers. There are currently about 140 to 150 refereed papers that have appeared or are in press. In next month's report we will present a summary and report recent titles. - Papers Published (2) - "Coherent Brightness Variations in Solar Radiative Output from the Photosphere to the Corona", J.L. Lean, J.T. Mariska, K.T. Strong, H.S. Hudson, L.W. Acton, G.J. Rottman, T.N. Woods, and R.C. Willson, G.R.L., 22, 655-658, 1995. "Comment on 'The Solar Flare Myth'", H.S. Hudson, B.M. Haisch, and K.T. Strong, J.G.R. 100, 3473-3477, 1995. - Papers accepted (1) - "Detection of Nonthermal Radio Emission from Coronal X-ray Jets," M. R. Kundu, J.-P. Raulin, N. Nitta, H. S. Hudson, M. Shimojo, K. Shibata, and A. Raoult, ApJ Letters. - Papers Submitted (2) - "Joint Radio and Soft X-ray Imaging of an "Anemone" Active Region," A. Vourlidas, T. S. Bastian, N. Nitta, and M. J. Aschwanden, Solar Physics "The Flare of 1992 August 17 23:58 UT," Masaaki Takahashi, Tetsuya Watanabe, Jun-ichi Sakai, Saku Tsuneta, Taro Sakao, Takeo Kosugi, Takashi Sakurai, Shinzo Enome, Nariaki Nitta, Hugh S. Hudson, and Shizuyo Hashimoto, PASJ. - Presentations (3) - "The Eruptive flare of 15 Nov 1991," Jean-Pierre Wuelser, ISAS Yohkoh seminar. "The 11 July 92 flare: a counter example to the loop-top blob paradigm?", James R. Lemen, ISAS Yohkoh seminar. "Yohkoh SXT Observations of Prominence Eruption or Disappearance", H. Tonooka, S.F. Martin, R.C. Canfield, K. Shibata, A. McAllister, K. Reardon, Japanese Astronomical Society Spring Meeting, March 20-24, 1995 - Abstracts submitted(3) - Page 4 "Comparison and Relation of He I 1083nm Two-Ribbon Flares and the Large-Scale Coronal Arcades Observed by Yohkoh SXT". (NSP/SP Summer Workshop on `Solar Drivers of Interplanetary and Terrestrial Disturbances'). K. L. Harvey, A. McAllister, H. Hudson, D. Alexander, J. Lemen. "Differential Rotation in the Solar Corona", M. Weber et al., to be presented at the 1995 SPD Meeting, Memphis. "Spatial relations between preflares and flares as derived from Yohkoh soft X-ray images", F. Farnik, H. Hudson, T. Watanabe, Solar Physics << Public Use of SXT Images >> Yohkoh/SXT images appeared in the March edition of Scientific American. We continue to submit and have published our monthly article on solar weather in "Sky & Telescope". << Yohkoh Operations and Health >> Yohkoh and the SXT continue to function well. No significant degradation in the instrument has occurred since the loss of the front thermal shield in 1992. SXT experienced a normal level of Single Event Upset (SEU) events during the month: SXT bitmap error 7-Apr-95 00:29 UT SXT bitmap error 20-Apr-95 09:30 UT SXT warm reset 25-APR-95 19:34 UT - recovered 26-APR-95 13:05 UT SXT bitmap error 27-Apr-95 13:22 UT The use of Wallops ground station has continued and has helped eliminate conflicts with the Japanese ASCA spacecraft. The Japanese SFU infra-red mission completed the operations of the IRTS instrument package this month as the cryogenic cooler has not run out of liquid helium. SFU has been given priority over Yohkoh and ASCA for Kagoshima ground station operations during the past three months. Page 5 << Data Flow >> ------------------------------------------------------------------------------ Month Full Frame Images Observing Region Images Received Lost Received Lost Loss % QT FL Tot Thru Jan-93 99152 47251 361331 174570 535901 196861 26.64 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 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 4570 1540 16789 3643 20432 6796 24.96 May-95 0 0 0 0 0 0 24.96 Total 289854 124322 1234262 343973 1578235 610820 27.90 Number of Full Frame Images Received: 289854 Number of Observing Region Images Received: 1578235 Total: 1868089 Approximate Number of Shutter Moves/CCD Readouts: 3258395 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 (%) 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 44.46 523.4 23020 2600 22.5 / 2 17.7 N/A Aug-93 44.20 513.6 21319 2598 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 46.00 580.9 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 48.64 679.9 92014 5542 19.1 N/A May-95 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-APR-95 and 30-APR-95 ACTON 29-APR-95 30-APR-95 * 2 (total of 2 days) FREELAND 1-APR-95 * 20-APR-95 20 (total of 20 days) HUDSON 3-APR-95 15-APR-95 13 22-APR-95 30-APR-95 * 9 (total of 22 days) LEMEN 3-APR-95 30-APR-95 * 28 (total of 28 days) STRONG 1-APR-95 * 1-APR-95 1 (total of 1 days) WEBER 1-APR-95 * 1-APR-95 1 (total of 1 days) WUELSER 11-APR-95 30-APR-95 * 20 (total of 20 days) ---------------------------------------------------------------- Grand Total of 94 days for 7 people NOTE: The "*" signifies travel that actually ends after 30-APR-95 SXT Foreign Travel between 1-MAY-95 and 31-MAY-95 ACTON 1-MAY-95 * 28-MAY-95 28 (total of 28 days) HUDSON 1-MAY-95 * 31-MAY-95 * 31 (total of 31 days) LEMEN 1-MAY-95 * 3-MAY-95 3 (total of 3 days) NITTA 26-MAY-95 31-MAY-95 * 6 (total of 6 days) SLATER 2-MAY-95 31-MAY-95 * 30 (total of 30 days) LABONTE 17-MAY-95 20-MAY-95 4 (total of 4 days) WUELSER 1-MAY-95 * 5-MAY-95 5 (total of 5 days) STURROCK 1-MAY-95 7-MAY-95 7 (total of 7 days) ---------------------------------------------------------------- Grand Total of 114 days for 8 people NOTE: The "*" signifies travel that actually ends after 31-MAY-95 Respectfully submitted, James R. Lemen Frank M. Friedlaender Page 8 =========================================================== Montana State Univ Activity Report for March and April 1995 =========================================================== This bimester the MSU group has continued to be involved with solar physics (in general) and Yohkoh SXT (in particular) on many different levels, including SXT operations, research, public outreach and education. MSU has had several visitors recently: Jack Gosling, Len Culhane, Louise Harra, and Sarah Matthews. In March, Acton found time to do some work on SXT calibration. Specifically, he derived expressions for the key SXT point-spread function (PSF) parameters as a function of the plasma temperature. Acton also worked on the slope of the SXT x-ray scattering function. Other calibration work focussed on the SFC work of Freeland and generation of the new SDM (averaged dark frames) data base with Mons Morrison. As for scientific collaboration, Acton has almost finished a paper with Terry Forbes and the analysis for a coronal temperatures paper with Sturrock, Culhane and Lemen. Forbes is presenting a paper on their cusped-loop work at the AGU and Sturrock and Acton are giving back to back papers at the SPD. Sturrock is also talking about this at IAU153 in Japan in May. Acton is working with Hugh Hudson and Sam Freeland on the 13-Nov-1994 eruptive flare. After a 4 day visit at MSU by Len Culhane to work on temperature structure of the corona, Acton made a trip to Boulder's HAO to give a talk on his 13-Nov-1994 eruptive flare analysis and to discuss solar physics in general. Acton also traveled 1775 miles of Montana talking with grade school students and high school teachers about science, space and the sun. Alexander has spent a good bit of his time in the preparation of the Physics of Astrophysics class he is currently teaching for the department. Furthermore, he played the role of host to two visitors to MSU: Louise Harra and Sarah Matthews. Harra visited from the University of Birmingham (April 4-14) on the NATO coronal heating project. Harra and Alexander devised a program which sequentially reads in the BCS data and produces integrated fluxes for each orbit in the database. The results of this analysis will be compared with the similar data obtained from SXT compiled by Loren Acton. Matthews visited from the University of Glasgow (April 10-23) for work on various non-thermal line broadening topics. With Louise Harra they began the task of looking at the non-thermal velocity (Vnt) signatures from various cusped flare events. Their aim is to compare the Vnt time development with the hard X-ray development and to carry out a comparison between the Vnt behavior for cusp events on the disk and limb. Matthews and Alexander also did some work on the 13-Jan-92 (home run) event. They are comparing the Vnt behavior with the time characteristics of the HXT footpoint and loop top sources. Alexander and Sergei Katsev, an undergraduate working with the MSU Solar Group, completed the first phase of their project to look at the effects of loop orientation on the interpretation of SXT images. Lastly, the Proceedings of 3rd SoHO Workshop finally arrived, with two papers by Alexander: "The Large Scale Coronal Eruptive Event of April 14 1994" D. Alexander et al., and "Differential Rotation in the Solar Corona", M. Weber et al. Page 9 Handy has spent most of his time at LPARL as the MSU Graduate Representative to the TRACE project. In addition to his duties managing the MSU/TRACE budget, Handy has made progress in writing the Technical Specifications for the optical components of the UV channel. For the science side of his thesis, Handy has been studying the 1992 and 1994 SPDE rocket flights with Bill Brown. Handy visited MSU at the end of April to install the ISASS4 (renamed Asahi in honor of Japanese beverages) workstation into the MSU Solar computer system. Simultaneously another 8 Gigabytes of disk storage were brought on line, and as a result two 2.1 Gb drives were liberated and will be sent to Japan with L. Acton at the first of May. Forty MB of RAM for the DECstations was acquired from a source on MSU campus at a discount price, so the new workstation now has 40 MB and SXT4 has 64 MB. As mentioned earlier in this report, undergraduate Sergei Katsev has joined the MSU Solar Group to work with D. Alexander on the effects of loop orientation on the interpretation of SXT images. Katsev presented this work at the MSU Undergraduate Scholars Program Conference. Katsev and Alexander plan to write a brief paper based on the talk for the Journal of Undergraduate Research and a fuller research paper for submission to Ap.J. Weber remained in Japan through the month of March, performing the job of Yohkoh SXT Chief Observer and took this opportunity to have many educational talks with Strong, Hudson, and others. During this period, Weber contributed to the development of a "terminator campaign", a part of the ongoing calibration efforts for SXT. Also, Weber applied for, and was awarded, an SPD Student travel Award to attend the 1995 SPD Meeting in Memphis and applied to renew his Montana Space Consortium Grant, which covers his stipend for the academic year. Upon return to MSU in April, Weber took up again his continuing research on the possible differential rotation of the corona, presented in preliminary form at the SoHO III workshop in Estes Park and published in the Proceedings of 3rd SoHO Workshop as "Differential Rotation in the Solar Corona", M. Weber et al. This same title has been submitted for presentation at the 1995 SPD Meeting. David Weston, a first-year physics graduate student at MSU, has joined the MSU Solar Group recently. His priorities right now are in preparing for the Physics Department Comprehensive Exams, to be given in June. After that, Weston will be working on various SXT calibration issues with Acton as summer research. Page 10 ================================================================ Univ of Calif, Berkeley Activity Report for March and April 1995 ================================================================ In the past two months, we have been extending our research into the relationships between soft and hard X-ray emission in impulsive footpoint sources. The results from this study, including results from the flares of 2-nov-91 and 26-jan-92, will be presented at the SPD meeting in June. The improvement over the previous work involving these footpoints lies in the increased reliability of the hard X-ray spectra, which are now obtained from HXT images given by a forward-fitting method. A given number of gaussian-shaped (or Moffat function-shaped) sources are fit to the HXT data, rather than using the Maximum Entropy deconvolution method (MEM). The MEM tends to underestimate the amount of hard X-ray flux in a given source; and the underestimation in the flux increases with increasing energy, resulting in spectra which are steeper than they should be. The MEM is still used to find the position and size of the footpoints. The work that we have done regarding the uncertainties in HXT spectra and SXT temperature measurements (now including the effects of possible sub-pixel alignment errors which may result in the smearing of sources) will be included. Page 11 ======================================================= Univ of Hawaii Activity Report for March and April 1995 ======================================================= Our most important activities included support of Yohkoh operations and data analysis at ISAS, coordinated ground-based data acquisition at Mees, including designated Yohkoh campaigns, analysis of Yohkoh/Mees data, and preparation of manuscripts, Operational support for SXT and designated campaigns was provided by Hudson and Wuelser at ISAS, by Judd, Nitta, and Douglass at Mees, and by Jiao, LaBonte, Metcalf, Reardon, and Wuelser in Manoa. A small amount of data was obtained for an X-ray bright point campaign led by K. Harvey, but poor weather prevented data from being obtained during the HRTS rocket campaign led by J. Cook. As solar activity continued to wane with the approach of solar minimum, Reardon took the opportunity to continue coordinating Yohkoh/SXT and ground-based observations of solar filaments. On at least three different occasions, Yohkoh and Mees Solar Observatory made joint observations of a selected filament. The SOONSPOT network of H-alpha telescopes also specially targeted the chosen filament several times in coordination with Yohkoh. Useful data were obtained in x-rays and visible light on the physical condition of the solar atmosphere surrounding the filament. Unfortunately, none of the selected filaments have yet provided the "Holy Grail" of the project, simultaneous and high time resolution observations of H-alpha spectra, vector magnetic fields, and soft-x-rays during a filament eruption. Reardon also did the first coalignments of observations with the Yohkoh SXT and the Mees H-alpha coronagraph. There were several interesting results, such as the continued propagation of a soft x-ray front long after the H-alpha emission has ended. This work, done in collaboration with Shibata, Martin, and Tonooka, was presented at the Japanese Astronomical Society Meeting in March. Reardon and Canfield finished up their analysis of the data on surges and jets in AR 7260 on 19 August, 1992. All figures for the paper are now completed, and the text is nearly ready for distribution to co-authors for their comments. Metcalf continued to work on IVM H-alpha data and completed a comparison of the IVM data to Nobeyama radioheliograph data. He also continued writing up the study. The number of analyzed flares is now up to 5. With a sufficiently large set of flares it will be possible to test the impact polarization hypothesis. Metcalf continued to work with J. Li on a study of the spatial Page 12 relationship between hard x-ray emission during flares and photospheric current systems. The study confirms that HXR emission normally occurs at the edges of vertical photospheric currents. Metcalf analyzed 5 magnetograms from 3 separate active regions for G. Doschek for his study of flares with strong blueshifts. He also began a co-alignment of some of the magnetograms with SXT data. Motivated by the Coordinated Data Analysis Workshop (CDAW) last fall, Wuelser started to work again on eruptive flares. These events are characterized by dynamic behavior in both soft X-rays and H-alpha, and associated radio type II bursts. The objective of the work is to establish the relationship between the dynamic flare component and the flare energy release. Wuelser selected a few events for the initial analysis (1991 November 15, 1992 January 30, 1992 July 16, 1994 January 14). He obtained some initial results for the 1991 November 15 event, and presented them at the Yohkoh seminar at ISAS. Among the preliminary findings are that this event clearly shows two eruptive episodes. The first episode is the filament eruption prior to the impulsive phase, and the second episode is associated with the impulsive hard X-ray burst. Both eruptive episodes show co-spatial moving material in H-alpha and in the soft X-rays. Hudson continued his work on the flare/CME relationship. It is becoming much clearer that Yohkoh sees CME launches more clearly than many persons think - the difficulty of seeing CME effects is partly due to the interruptions in the standard movie resulting from flare triggers. In particular the coronal disappearance observed just prior to the 21 Feb. 1992 event (the celebrated Yohkoh "Candle Flame" flare) is now being interpreted as a CME launching, and its morphology is quite interesting. The outward motion of the coronal material clearly goes into a much larger range of position angle than the flare itself, which may help to explain the often-cited mismatch between flare and CME sizes. In other projects, Hudson helped with papers on type III bursts (Kundu, Raulin), on flare studies (Nitta, Gopalswamy), and on "giant arches" (Svestka). In the course of this work F. Farnik found, and Hudson confirmed, a tendency for the giant arches to increase in temperature with height and age. This is the opposite of post-flare loops, and is all the more striking in that the giant arches occur long after the post-flare loops have subsided. Finally, Hudson attended the Solar Radio Telescope workshop in San Juan Capistrano. Canfield worked on the analysis of surges and jets in AR 7260 and a manuscript describing their interpretation, in collaboration with Reardon, Leka, Yokoyama, Shibata, and Page 13 Shimojo. He worked with A. Pevtsov on the magnetic helicity of structures in the corona, as seen in SXT data; he and Pevtsov are comparing the sign of helicity implied by SXT structures to that derived from the Mees vector magnetograms. PLANS FOR MAY AND JUNE Canfield will finish the paper on surges and jets in AR 7260 and distribute it to colleagues for comments. He will prepare and deliver a paper on this topic at IAU Colloquium 153 in Tokyo in May. He will prepare and deliver a paper on Yohkoh evidence for magnetic reconnection at the Spring AGU meeting in late May. In June he will begin a manuscript with Reardon on reconnection events prior to filament eruptions. Hudson will assist F. Farnik (BCS) and T. Watanabe (NAOJ) in analysis of hard-spectrum events. This work will incorporate some ideas about "impulse response" compact events, of the type found by White et al. (Ap. J. 1992), and will be presented at the SPD meeting in Memphis. In the meanwhile Hudson will be busy in May with arrangements and preparations for IAU Colloquium #153, which will take place in Tokyo. In June Hudson intends to resume work on a review of solar X-rays, to be co-authored with L. Culhane (MSSL). Wuelser will continue the study of eruptive events, and plans to present a poster on this topic at the Solar Physics division meeting in Memphis. Metcalf will continue the analysis of the IVM H-alpha polarization data and the associated manuscript. He will start work on a new version of the SXT pixon code. He will continue collaborations with J. Li and G. Doschek. Reardon will continue to look for good filament targets for the joint SXT and Mees observations, do more coalignments between SXT data and Mees H-alpha coronagraph observations to develop a larger dataset of limb events, and work with Canfield on "tether cutting" events. PUBLICATIONS AND PRESENTATIONS DURING MARCH AND APRIL Papers submitted "Metric type III bursts associated with soft X-ray jets", J.P. Raulin, M.R. Kundu, H.S. Hudson, N. Nitta, and A. Raoult, Ap. J. "Solar flares: no myth", H.S. Hudson, EOS "Spatial relations between preflares and flares as derived from Yohkoh soft X-ray images", F. Farnik, H. Hudson, T. Watanabe, Solar Physics Page 14 Papers published "Coherent brightness variations in solar radiative output from the photosphere to the corona", J.L. Lean, J.T. Mariska, K.T. Strong, H.S. Hudson, L.W. Acton, G.J. Rottman, T.N. Woods, and R.C. Willson, G.R.L., 22, 655-658, 1995. "Comment on 'The Solar Flare Myth'", H.S. Hudson, B.M. Haisch, and K.T. Strong, J.G.R. 100, 3473-3477, 1995. Presentations given "Yohkoh SXT Observations of Prominence Eruption or Disappearance", H. Tonooka, S.F. Martin, R.C. Canfield, K. Shibata, A. McAllister, K. Reardon, Japanese Astronomical Society Spring Meeting, March 20-24, 1995 Page 15 ====================================================== Stanford Univ Activity Report for March and April 1995 ====================================================== Peter Sturrock is continuing work with Loren Acton in analyzing SXT data for a region of the diffuse corona that was observed on May 7-9, 1992. Sturrock has developed a model corona that is spherically symmetric, involves an inward heat flux, and that so far neglects energy losses by radiation. He finds that it is possible to get a good fit to the count rates in the Al1 and AlMg bands for the following choice of parameters: base temperature = 10^6 K; base density = 10^8.8 cm^-3; and inward heat flux = 10^6.6 erg cm^-2s^-1. Sturrock will be comparing the data with other models (including an assembly of loops), and extending the present model to take account of energy loss by radiation. George Roumeliotis worked on an article that develops the idea that the plasma in coronal loops is heated in electric current sheets. With relatively few free parameters, the theory predicts the high temperature loop plasma seen by Yohkoh. The theory also predicts small filling factors, on the order of 0.001. This is consistent with recent work by Klimchuk and Porter, who estimated the filling factor of coronal loops based on observed cooling times. Mike Wheatland continued looking at hard X-ray images reconstructed for a sample of flares, with emphasis on the appearance of a coronal hard X-ray source identified in some (limb) flares, in the rise, or at or near the peak phase. In particular he has been trying to characterize the time history of X-ray emission in these flares. The goal is to precisely define what a model of the X-ray emission needs to account for, and to decide if existing models are adequate, or if a new formulation is needed. On March 13, Jim Klimchuk presented his work with Lisa Porter on "Soft X-Ray Loops and Coronal Heating" at the NASA/Goddard Workshop on Wave Heating. He attended the Solar Radio Telescope Workshop in April and discussed his work with Dale Gary comparing SXT and OVRO microwave measurements of temperatures and emission measures in active regions. He also submitted abstracts for the spring AGU and summer SPD meetings entitled "The Heating of Coronal Loops" and "The Cross Sectional Properties of Coronal Loops," respectively. Klimchuk continued his recent work with Peter Cargill in which coronal loops observed by SXT are simulated with a simple episodic (nanoflare) coronal heating model. After being impulsively heated, the loops evolve through two stages: an evaporative cooling stage in which the loops cool by thermal conduction, and a condensation cooling stage in which the loops cool by radiation. During both stages, there is an exchange of material with the chromosphere. The initial results are promising. Klimchuk recently began a project to detect the occurrence of Earthward-directed coronal mass ejections (CMEs). The idea is to identify Page 16 the formation of closed arcades that typically occur shortly after a CME has opened the coronal field. This includes the very bright arcades that produce long duration events (LDEs) in the full disk GOES X-ray signal, as well as fainter arcades which are not obvious above the background in the GOES record. It is hoped that the end product will be a functional algorithm for predicting the occurrence of geomagnetic disturbances. Page 17 ===================================================================== Solar Physics Research Corp. Activity Report for March and April 1995 ===================================================================== (Karen L. Harvey) Activity the last two months are as follows: (1) Established a general study with Alan McAllister, Hugh Hudson, David Alexander, and Jim Lemen to investigate the comparison and association of large scale coronal arcades and two-ribbon flares observed in the NSO/KP He I 10830 data. The results of this study will be presented at the National Solar Observatory/Sacramento Peak Summer Workshop to be held October 16-20, 1995. Title of paper to be presented this group is "Comparison and Relation of He I 1083nm Two-Ribbon Flares and the Large-Scale Coronal Arcades Observed by Yohkoh SXT". (2) Attempted another collaborative XBP campaign from 19 - 26 April 1995, involving Yohkoh SXT, BBSO, MSO, NSO/KP. The objective of this particular campaign was to obtain He I 10830 and magnetic field observations simultaneously with the high spatial and temporal SXT X-ray observations. High solar activity delayed the start of the XBP campaign. Combined with poor weather, this run turned out to be unsuccessful in meeting our goals. We will try again in mid-June. (3) Preparation of NSO/KP full-disk magnetograms and He I 10830 spectromagnetograms for SXT investigators for studies of the magnetic field and He I 10830 structures associated with X-ray Jets and large scale X-ray arcades. (4) Continued preparation of invited paper to be given at the SolWind 8 meeting in late June. Title: "Coronal Structures Deduced from Photospheric Magnetic Field and He I 10830 Observations". This paper will discuss the behavior of the magnetic fields in the photosphere and those inferred for the corona. Events and structures specifically addressed will be coronal holes and large scale two-ribbon flares seen in He I 10830 and their comparison with the Yohkoh SXT data. (5) Continued reduction of observations obtained in collaboration by Yohkoh SXT, NSO/KP, BBSO, and MSO during the XBP campaigns. This includes the registration and cleaning up of the SXT PFIs and registration and co-alignment of the simultaneous NSO/KP magnetograms and He I 10830 spectroheliograms of the target areas with the SXT data. (6) Continued collection and updating of the bibliography of Yohkoh papers. Abstracts submitted: "Comparison and Relation of He I 1083nm Two-Ribbon Flares and the Large-Scale Coronal Arcades Observed by Yohkoh SXT". (NSP/SP Summer Workshop on `Solar Drivers of Interplanetary and Page 18 Terrestrial Disturbances'). Authors: K. L. Harvey, A. McAllister, H. Hudson, D. Alexander, J. Lemen. 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 May 1995 April 1995 |------------------------------- | 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 - 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 1995 |------------------------------- |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