Page 1 PROGRESS REPORT THE SOLAR-A SOFT X-RAY TELESCOPE (SXT) PROGRAM (CONTRACT NAS8-37334) (for February 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 new Alpha workstations for Japan were installed by Gary Linford and Lawrence Shing. This was a major transition involving the replacement of the ISASS0, the principal file server for Yohkoh software and data bases. The transition has gone well. The reformatter runs approximately three to four times faster on the new workstations. An outstanding item for the month is the marked reduction in value of the dollar against the Japanese Yen. Although our total exposure is probably less than $200,000 per year, an annual penalty of 20% is not insignificant. We interviewed applicants for the Post-doc position that was advertised. It is expected that an offer will be made during March. << Solar Activity >> Solar activity was slightly enhanced during February, compared with the previous month. Towards the end of January, AR 7834 appeared on the east limb. This active region is probably the return of AR7823. This region produced several C flares and 3 M-class flares during the first week of February. Solar activity then became moderate for a couple of weeks, hovering at about B1 Goes level. Late in the month AR 7844 appeared and produced many C flares and then culminated its efforts with a M1.1 flare. There were 28 flares that were C1-class or greater << Campaigns >> Page 2 At the beginning of the month SXT continued a coordinated observing campaign with NSO (Sac Peak and Kitt Peak) organized by Roberto Falciani and Gino Smaldone. The objective of the campaign was to observe bright points and other features associated with the decay of the solar cycle. The end of the observing campaign was hampered by cloudy weather. On 20 February Yohkoh supported a VLA observation coordinated by Arnold Benz to make a multi-frequency observation of the quiet Sun on the disk. Yohkoh images were used by Benz to select the region of observation. For the period of overlap the SXT data were quite good. << Science >> There were no scientific meetings during February. Several presentations made at various science seminars. We are beginning to prepare for the several meetings that will occur during the spinrg (2 IAU meetings, AGU, ASS-SPD, Solar Wind-8). Several papers were submitted this month and it appears that there are several other papers that will be completed and submitted in the near future. << Publications>> The following list is an incomplete listing of work in progress on papers and presentations that include scientists that are supported by the NASA SXT contract. - Papers Published (2) - "Is the Solar Chromospheric Magnetic Field Force-Free?", Thomas R. Metcalf, Litao Jiao, Han Uitenbroek, Alexander N. McClymont, and Richard C. Canfield, Astrophys. J., 439, 474. "Resolving the 180 Degree Ambiguity in Vector Magnetic Field Measurements: The 'Minimum' Energy Solution," Thomas R. Metcalf, Solar Phys., 155, 235. - Papers accepted (1) - "A Comparison of Active Region Temperatures and Emission Measures Observed in Soft X-Rays and Microwaves and Implications for Coronal Heating," by Klimchuk, J. A. and Gary, D. E., accepted by ApJ. - Presentations (5) - "The LDE event of 13 Nov. 1994: a CME launch?", H.S. Hudson, seminar presentation at ISAS, 5 January 1995 (invited). Page 3 "Yohkoh and Ulysses Observations of CMEs Feb.-Apr. 1994," H.S. Hudson, STEP Data Analysis Symposium (Toyokawa, Japan) 18 Jan. 1995 (invited). "Flares and CMEs," H.S. Hudson, Feb. Mitaka meeting 6-8 Feb. (contributed). "High-resolution Imaging of the Solar Corona," K. T. Strong, seminar presentation at Center for EUV Astrophysics, Berkeley, 10 Feb. 1995 (invited). "A Comparison of Active Region Temperatures and Emission Measures Observed in Soft X-Rays and Microwaves and Implications for Coronal Heating," K. T. Strong, NASA/Goddard Space Flight Center. - Abstracts submitted(7) - "X-ray Bright Point Flares Due to Magnetic Reconnection," L. van Driel-Gesztelyi, B. Schmieder, N. Mein, A. Hoffmann, N. Nitta, G. Cauzzi, H. Kurokawa, G. Kawai, P. Mein, J. Staiger, submitted to A & Ap, January 1995. "Detection of Nonthermal Radio Emission from Coronal X-ray Jets," M.R. Kundu, J.-P. Raulin, N. Nitta, H.S. Hudson, M. Shimojo, A. Raoult and K. Shibata, submitted to ApJ Letters, February 1995. "Detection of nonthermal radio emission from coronal X-ray jets," M.R. Kundu, J.P. Raulin, H.S. Hudson, N. Nitta, M. Shimojo, and A. Raoult, submitted to Ap. J., February, 1995. "Yohkoh soft X-ray spectroscopic observations of the bright loop-top kernels of solar flares," J.I. Khan, L. Harra-Murnion, H.S. Hudson, J.R. Lemen, and A.C. Sterling, submitted to Ap. J. (Lett). February, 1995. "A Search for Asymmetric Flows in Young Active Regions", G. Cauzzi, R. C. Canfield, and G. H. Fisher, submitted to Ap. J. February, 1995. "Soft X-Ray Loops and Coronal Heating," by Porter, L. J. and Klimchuk, J. A., submitted to ApJ. "The Heating of Coronal Loops," by Klimchuk, J. A. and Porter, L. J., submitted to Nature. << Public Use of SXT Images >> We continue to submit and have published our monthly article on solar weather in "Sky & Telescope". Gary Linford and Keith Strong put together a composite image for Scientific American showing the change in the output of the solar corona in the 42 months of observations since the launch of Yohkoh. Loren Acton and Keith Strong helped Sasha Nemichek, a member of the Scientific American staff, write a short Page 4 caption/article to go with the image. The article will appear in the April issue. Solar images taken with the Yohkoh/SXT have appeared in various publications recently. An SXT software image appeared on the cover of the February 1995 edition of NASA Tech Briefs. In the February 6, 1995, edition of Newsweek, an SXT x-ray image was included in a short article on the Cyberscope page which also described how Yohkoh data was available from the Goddard World Wide Web home page. Finally, the British Magazine, Astronomy Now, featured a series of images taken during the solar eclipse last November which was a partial eclipse as seen at the Yohkoh spacecraft. << Yohkoh Operations and Health >> Yohkoh and the SXT continue to function well with no Single Event Upsets (SEUs). No significant degradation in the instrument has occurred since the loss of the front thermal shield in 1992. There were no bitmap errors reported during this month. The Wallops station has recently been incorporated into the DSN system. Yohkoh has begun to use the Wallops station for downlink, however, the planning and operational software is not yet fully equipped to handle Wallops commanding or data. Software modifications will be made next month. Page 5 << Data Flow >> ------------------------------------------------------------------------------ Month Full Frame Images Observing Region Images Received Lost Received Lost Loss % QT FL Tot Thru Oct-92 78850 37943 288731 148277 437008 158479 26.31 Nov-92 6648 2949 24345 14832 39177 12859 24.71 Dec-92 6766 3008 24188 6600 30788 12454 28.80 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 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 2922 887 11115 105 11220 3793 25.26 Total 268865 116693 1157365 331463 1488828 579010 28.00 Number of Full Frame Images Received: 268865 Number of Observing Region Images Received: 1488828 Total: 1757693 Approximate Number of Shutter Moves/CCD Readouts: 3060403 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 (%) 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 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 47.02 619.0 58434 4121 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 48.66 680.8 91597 5716 20.9 N/A Mar-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-FEB-95 and 28-FEB-95 ACTON 4-FEB-95 28-FEB-95 * 25 (total of 25 days) HUDSON 1-FEB-95 * 28-FEB-95 * 28 (total of 28 days) LEMEN 1-FEB-95 * 5-FEB-95 5 (total of 5 days) LINFORD 13-FEB-95 28-FEB-95 * 16 (total of 16 days) SHING 13-FEB-95 28-FEB-95 * 16 (total of 16 days) SLATER 1-FEB-95 * 4-FEB-95 4 (total of 4 days) WEBER 4-FEB-95 28-FEB-95 * 25 (total of 25 days) CANFIELD 1-FEB-95 * 11-FEB-95 11 (total of 11 days) MCTIERNAN 9-FEB-95 25-FEB-95 17 (total of 17 days) ---------------------------------------------------------------- Grand Total of 147 days for 9 people NOTE: The "*" signifies travel that actually ends after 28-FEB-95 SXT Foreign Travel between 1-MAR-95 and 31-MAR-95 ACTON 1-MAR-95 * 4-MAR-95 4 (total of 4 days) FREELAND 14-MAR-95 31-MAR-95 * 18 (total of 18 days) HUDSON 1-MAR-95 * 1-MAR-95 1 12-MAR-95 31-MAR-95 * 20 (total of 21 days) LINFORD 1-MAR-95 * 15-MAR-95 15 (total of 15 days) SHING 1-MAR-95 * 15-MAR-95 15 (total of 15 days) STRONG 1-MAR-95 31-MAR-95 31 (total of 31 days) WEBER 1-MAR-95 * 31-MAR-95 * 31 (total of 31 days) ---------------------------------------------------------------- Grand Total of 135 days for 7 people NOTE: The "*" signifies travel that actually ends after 31-MAR-95 Respectfully submitted, James R. Lemen Frank Friedlaender Page 8 ====================================================================== Montana State University Activity Report for January and February 1995 ====================================================================== During Jan-Feb the MSU group has been involved in SXT operations, research, public outreach and education. The upgrade of storage capacity of our computer/data analysis system to a total of 17 Gb has been completed -- funded by our IDC budget. In January we were favored by an enjoyable and productive 3 day visit by Jack Gosling of Los Alamos National Laboratory. Jack gave an excellent and well attended Physics Colloquium on, "An Interplanetary View of Solar Coronal Mass Ejections". Good progress was made on a proposal with Nancy Crocker and Jo Ann Joselyn for a Chapman Conference at MSU in the summer of 1996 on "Coronal Mass Ejections: Causes and Consequences". MSU is contributing $10K towards the cost of the conference! A summary of activities of each of the members of the MSU group are as follows. Acton continues to work on analysis for the cusped flare paper with Terry Forbes and the coronal heating paper with Sturrock, Culhane and Hudson. Other work in progress includes publication of the SXT irradiance data with White, the 13 Nov 1994 CME/Flare paper with Hudson and Freeland and modeling of the uncertainties of SXT irradiance values caused by our limited wavelength coverage and isothermal approximation with Bruner. Acton spent the month of February at ISAS as SXT Chief Observer and concentrated on issues connected with straylight correction. He also agreed to present invited papers at IAU153 in May in Japan, the IAGA meeting at Boulder in July and at the Cool Star Workshop at Florence, Italy, in October -- and will give a contributed paper at the AAS-Solar Physics Division meeting in Memphis in June. Alexander has interacted with John Brown of University of Glasgow on possible collaboration between UoG, MSU and NAOJ combining theoretical studies with Yohkoh data, and continued discussion of SXV/SXT combined analysis with Louise Harra for NATO funded project. Louise will visit MSU in early April. Good progress is being made on his loop geometry project, which should help bridge the gap between loop models and SXT data, with undergraduate student Sergei Katsev. His short article for the Cyberscope section of NEWSWEEK with an SXT image caused a rush of activity at the GSFC/SDAC mosaic page. He submitted abstracts on his work on the 14 April 1994 polar crown event for the Solar Wind 8 meeting and the spring AGU. Alexander presented two community education classes in the Willson High School in Bozeman and began teaching "The Physics of Astrophysics" graduate course here at MSU. Handy is now spending most of his time on the TRACE program at LPARL but continues to help with support of the SXT analysis system. Ragenovich is now concentrating on the visualization aspects of her master's thesis program so we are seeing less of her for the moment. Weber continues with his thesis work on coronal differential rotation -- much of the SFD data that he needs is now on-line thanks to our increased Page 9 disk capacity and the work of Katsev reading tapes. He has worked on our movie making capability on the laser disk. Despite a great deal of effort this system is still not fully doing what we want. Weber spent February at ISAS as Chief Observer in training, analyzer of SXT pointing information and Yohkoh Toban at the SSOC for one week. =========================================================================== University of Calif, Berkeley Activity Report for January and February 1995 =========================================================================== In the last two months, our SXT work has concentrated on the uncertainty in data number due to uncertainties in dark current subtraction and alignment of images. The effects of compression uncertainties in dark current have been included in the online routines GET_DC_IMAGE and DARK_SUB, and SXT_PREP. The dark current uncertainty has little effect, it turns out. Also we have calculated the effect of uncertainty in alignment coordinates on data numbers and temperatures. This is possibly a larger effect, in particular for small sources; for an uncertainty in alignment of 0.1 pixels, the DN uncertainty can approach 10%. The major contribution to uncertainties in temperature measurement is still photon statistics. On a recent trip to ISAS, J. McTiernan completed a survey of the average temperature and total emission measure for 1261 SXT flares, effectively every available Be119-Al12 flare-mode filter pair for the mission, from 11-Oct-91 to 13-Dec-94. A report based on the analysis of this data may be presented at the upcoming SPD meeting in Memphis in June. Page 10 ================================================================== University of Hawaii Activity Report for January and February 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 Canfield (as SSOC toban) at ISAS, by Judd, Nitta, and Douglass at Mees, and by Canfield, Jiao, LaBonte, Metcalf, Reardon, and Wuelser in Manoa. Campaigns included an X-ray bright point campaign led by K. Harvey in January, a filament-eruption campaign led by Reardon that was run as a background program at Mees whenever conditions were appropriate during January and February, a campaign on tiny events led by R. Falciani and G. Smaldone at NSO/SP in early February, and a VLA campaign led by the Maryland group in mid-February. Jiao is working as a Teaching Assistant this semester, so is not formally working on the Yohkoh project. Nevertheless, he was able to make progress on his thesis, for which he will compare coronal structures observed by SXT to theoretical force-free coronal field lines from a model based on Mees vector magnetograms. During this period he wrote pre-processing software to prepare Mees and KPNO magnetograms for input to the MHD code that computes the theoretical coronal magnetic fields. This IDL software imbeds MSO and KPNO magnetograms into a single heliographic grid, in a form suitable for use by the supercomputer on which the MHD code is run. He also worked on post-processing IDL software for field line tracing and comparison of computed field lines to images, which will be used for analysis after the MHD code has been run. Also, for the use of the Yohkoh duty scientist at Mees, Jiao made an IDL program for filament campaigns. Reardon continued working with Shibata and Martin on the coregistration of SXT images with the Hydrogen-alpha coronagraph data from Mees Solar Observatory that they began at the Coordinated Data Analysis Workshop last October. The goal of the project is to compare the appearance of eruptive, and quasi-eruptive, events at the solar limb in soft x-rays and H-alpha. This will allow the comparison of two different temperature regimes (2,000,000 K and 10,000 K, respectively) in these eruptive events. They have identified 7 events over the past three years that have good simultaneous observations by both SXT and Mees. Reardon also worked with Hudson, Alexander, and Acton in joint observations of filaments on the solar disk with SXT on Yohkoh and the MCCD and IVM at Mees. The campaign involved special, long-exposure, filament observations with the SXT and magnetic field and H-alpha spectraheliogram observations from Mees. In addition, Alan Kiplinger also coordinated SOONSPOT H-alpha observations of the chosen H-alpha target. Several promising filaments were followed by the various observatories, including one filament which erupted at 20:00 UT on January 5 and was observed by the Mees instruments and SXT. Page 11 Metcalf worked on several projects during the reporting period. He continued to work on IVM H-alpha data and began a comparison of the IVM data to Nobeyama radioheliograph data. He also continued writing up the study. He completed a study of the affect of spatial resolution and filling factor on the resolution of the 180 degree ambiguity in vector magnetograms. He analyzed HSP and MCCD data from AR 7276 for Haimin Wang (BBSO) for his study of a flare on 1992 September 10. He continued to work with J. Li (IFA) on a study of the spatial relationship between hard x-ray emission during flares and photospheric current systems. The study confirms that HXR emission normally occurs at the edges of photospheric currents. He did a preliminary examination of HSP data for AR 7031 and AR 7123 for a collaboration with D. Gomez (IAFE, Argentina) on the relation between flares and magnetic separatrices. Finally, he made a comparison of the 3 HXT image reconstruction algorithms (Pixons, Maximum Entropy, and Direct Inversion) for a review paper being written by R. Puetter (UCSD). The figure is available on show_pix (misc/hxt920820). Wuelser worked on the chromospheric evaporation and energetics study. One of its central points is a comparison of predicted and observed chromospheric velocities, which requires observations of flares near disk center for which Yohkoh preflare data exist. Several such flares were identified and added to the study. Mickey and Wuelser participated in a week of maintenance work at Mees Observatory. One of the main tasks was the complete re-alignment and mechanical check of the 10 inch Coude refractor. This work should improve the image quality and reduce the image drift during observations that cannot use the sunspot tracker. This capability is important to our support of Yohkoh during this phase of the solar cycle around solar minimum. Hudson devoted much of his scientific effort to studying the Yohkoh counterparts of CME's. The main impetus for this has been the remarkable discoveries made by Ulysses during its polar passage, and the equally remarkable discoveries of the CME sources in the X-ray corona viewed by Yohkoh. Several abstracts were prepared for the Solar Wind 8 conference this summer. One highlight of the Yohkoh studies has been the realization that SXT actually sees disappearing coronal mass that must participate in the CME flow. In one well-observed event, an LDE flare of 13 Nov. 1994 was found to "launch" a mass > 4 x 10^14 g, interestingly enough at a time well after the soft X-ray flare onset. In another project, the initial paper on over-the-limb flares seen by BCS (and the other Yohkoh instruments) was completed and sent to Ap. J. (Letters). The main result is the discovery of non-thermal broadening of the X-ray emission lines localized to the loop tops during the impulsive phase. This implies a close connection of the loop tops with the fundamental energy release site. Finally, Hudson helped with the interesting discoveries being made by Kundu, Raulin et al. that associate soft X-ray jets with type III bursts. Page 12 Canfield spent four weeks in Japan, during which he participated in discussions about Stokes Polarimetry at a meeting at NAOJ and collaborated with K. Shibata and T. Yokoyama (NAOJ) and Reardon on SXT and Mees observations of X-ray jets and H-alpha surges in AR 7260. They worked on a manuscript and developed interpretations of their observations in terms of both upward and downward jets at the site of coronal reconnection. Canfield also started a project with A. Pevtsov (IFA) on the relationship between the vorticity of coronal structures observed by SXT and the average magnetic helicity observed in the photosphere by the Stokes Polarimeter at Mees. Finally, he finished a project led by G. Cauzzi (IFA) in which Mees and Yohkoh data were used to discover a flow asymmetry, opposite from theoretical predictions, in emerging flux regions. PLANS FOR MARCH AND APRIL Jiao will prepare a co-registered magnetogram dataset and run it on the Cray in San Diego, as his Teaching Assistant duties permit, Metcalf will continue his analysis of the IVM H-alpha polarization data in conjunction with the Nobeyama observations. He will also start work on a new version of the SXT pixon code and continue his collaborations with J. Li and D. Gomez. Wuelser will continue his chromospheric evaporation and energetics study. He will spend the month of April at ISAS in Japan. Hudson will assist Wuelser on the analysis of the Mercury transit data, and F. Farnik (BCS) and T. Watanabe (NAOJ) in analysis of hard-spectrum events and soft X-ray precursors. A paper with L. Acton and S. Freeland (LPARL) on the 13 Nov. event will be submitted. He will present an invited talk to a union meeting of geophysicists in Japan, on the subject of Yohkoh observations of magnetic reconnection. Hudson will also start work on a review of solar X-rays, to be co-authored with L. Culhane (MSSL). Reardon will help finish the paper on surges and jets in AR7260 and send it off for publication. He also plans to continue working on the comparison of H-alpha coronagraph and SXT images and prepare the results for presentation at an upcoming meeting. In addition, he will keep looking for suitable filaments for another joint observation program between SXT and Mees. Finally, he hopes to begin working on the manuscript for the tether-cutting episodes seen prior to the November 15, 1991 flare and filament eruption. Canfield will work on the paper on surges and jets in AR 7260 and on the comparison of coronal vorticity and photospheric magnetic helicity of solar active regions (with Pevtsov). PUBLICATIONS AND PRESENTATIONS DURING JANUARY AND FEBRUARY Papers submitted Page 13 "Detection of nonthermal radio emission from coronal X-ray jets", M.R. Kundu, J.P. Raulin, H.S. Hudson, N. Nitta, M. Shimojo, and A. Raoult, submitted to Ap. J., February, 1995. "Yohkoh soft X-ray spectroscopic observations of the bright loop-top kernels of solar flares", J.I. Khan, L. Harra-Murnion, H.S. Hudson, J.R. Lemen, and A.C. Sterling, submitted to Ap. J. (Lett). February, 1995. "A Search for Asymmetric Flows in Young Active Regions", G. Cauzzi, R. C. Canfield, and G. H. Fisher, submitted to Ap. J. February, 1995. Papers published "Is the Solar Chromospheric Magnetic Field Force-Free?", Thomas R. Metcalf, Litao Jiao, Han Uitenbroek, Alexander N. McClymont, and Richard C. Canfield, Astrophys. J., 439, 474. "Resolving the 180 Degree Ambiguity in Vector Magnetic Field Measurements: The 'Minimum' Energy Solution", Thomas R. Metcalf, Solar Phys., 155, 235. Presentations given "The LDE event of 13 Nov. 1994: a CME launch?", H.S. Hudson, seminar presentation at ISAS, 5 January 1995 (invited). "Yohkoh and Ulysses Observations of CMEs Feb.-Apr. 1994", H.S. Hudson, STEP Data Analysis Symposium (Toyokawa, Japan) 18 Jan. 1995 (invited). "Flares and CMEs", H.S. Hudson, Feb. Mitaka meeting 6-8 Feb. (contributed). Page 14 ================================================================= Stanford University Activity Report for January and February 1995 ================================================================= Peter Sturrock has been collaborating with Loren Acton in the analysis of temperature and emission-measure data for a radial scan through a quiet coronal region. He finds that the radial variation may be understood, to good approximation, on the basis of a spherically-symmetric isothermal corona. However, the temperature is found to increase with height. The dependence of temperature on radius seems to be compatible with a conserved inward heat flux. It appears, therefore, that the corona in this region is being heated by energy that originates more than one-half a solar radius above the surface. The analysis is continuing. A new post doc, Mike Wheatland, has joined our group. He will be looking at the correspondence between simultaneous HXT and SXT images of flares, particularly limb flares. His interest is with the loop-top hard X-ray sources identified in limb flares by Masuda (1993), and the relationships between these sources and the corresponding footpoint sources. Slava Glukhov has been considering the possibility that some of the elongated bright structures seen in SXT images may represent sheets of hot plasma, rather than loops. He has modeled what one would expect to see from a curved, X-ray emitting sheet of plasma, and the results conform to what SXT observes at the edges of active regions. Most of Klimchuk's time was spent preparing two publications describing his work with Lisa Porter on the dependence of loop pressure on loop length and its implications for the dependence of the volumetric heating rate on loop length. "The Heating of Coronal Loops" (Klimchuk and Porter) was submitted to Nature, and "Soft X-Ray Loops and Coronal Heating" (Porter and Klimchuk) was submitted to the Astrophysical Journal. The results appear to be consistent with heating by the dissipation of DC electric currents, but inconsistent with heating by the resonance absorption of Alfven waves. Klimchuk presented his work with Dale Gary at a seminar at the Goddard Space Flight Center entitled "A Comparison of Active Region Temperatures and Emission Measures Observed in Soft X-Rays and Microwaves and Implications for Coronal Heating." His paper by the same title was accepted for publication in the Astrophysical Journal. Klimchuk also began a collaboration with Peter Cargill that involves simulation of coronal loops heated by nanoflares and comparison with Yohkoh observations. Roumeliotis began a study on the spatial and temporal evolution of soft X-rays leading up to a solar flare. He is looking for reliable empirical signatures of imminent flare activity. Page 15 ========================================================================== Solar Physics Research Corp. Activity Report for January and February 1995 ========================================================================== Karen L. Harvey Activity the last two months are as follows: (1) Work on the analysis of the 14 April 1994 arcade event with David Alexander, Hugh Hudson, and Alan McAllister. Specifically looking at the evolution of the coronal holes located on either side of this event and of the underlying magnetic field over a several rotation interval around the time of this event. (2) 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. (3) Began preparation of invited paper to be given at the SolWind 8 meeting in late June. Abstract submitted: Coronal Structures Deduced from Photospheric Magnetic Field and He I 10830 Observations Karen L. Harvey (Solar Physics Research Corp., Tucson, AZ 85718) The National Solar Observatory synoptic program provides an extensive and unique data base of high-resolution full-disk observations of the line-of-sight photospheric magnetic fields and of the He I 10830 equivalent width. These data have been taken nearly daily for more than 21 years since 1974 and provide the opportunity to investigate the behavior of the magnetic fields in the photosphere and those inferred for the corona spanning on the time scales of a day to that of a solar cycle. The intensity of structures observed in He I \la~ are strongly modulated by overlying coronal radiation; areas with low coronal emission are generally brighter in He I 10830, while with high coronal emission are darker. For this reason, He I 10830 was selected in the mid-1970s as way to identify and monitor coronal holes, magnetic fields with an open configuration and the sources of high-speed solar wind streams. The He I spectroheliograms also show a wide variety of other structures from small-scale, short-lived dark points ($<$30 arc-sec, hours) to the large-scale, long-lived two `ribbon' flare events that follow the filament eruptions (1000 arc-sec, days). Such structures provide clues about the connections and changes in the large-scale coronal magnetic fields that are rooted in concentrations of magnetic network and active regions in the photosphere. In this paper, what observations of the photospheric magnetic field and Page 16 He I 10830 can tell us about the short- and long-term evolution of the coronal magnetic fields will be discussed, focusing on the quiet Sun and coronal holes. These data and what we infer from them will be compared with direct observations of the coronal structure from the Yohkoh Soft X-ray Telescope. (4) 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. (4) Preparation of NSO/KP magnetograms and He I 10830 spectroheliograms for several investigators involved in analysis of SXT data. (5) Continued collection and updating of the bibliography of Yohkoh papers. 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 | 10 March 1995 February 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 February 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 | 17 | ------------------------|------------------------|-----------------|----------- For sale by: Superintendent of Documents, U.S. Government Printing Office