Page 1 PROGRESS REPORT THE SOLAR-A SOFT X-RAY TELESCOPE (SXT) PROGRAM (CONTRACT NAS8-40801) (for January 1999) 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 Martin, 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 Martin Solar and Astrophysics 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 option to continue Data Analysis through January 26, 2000 was received from MSFC as well as the supporting funding. Pre-negotiations for continued operations during the same interval have also been initiated. It is expected that the contract modification will be completely definitized in February. << Solar Activity >> In early January, solar activity decreased precipitously owing to the rotation beyond the West limb of the huge region AR 8421. Much to our surprise, an over-the-limb event then occurred on the South, not the North, from the equally rotated but not so impressive AR 8422. Following the sharp decline around Jan. 8, activity rose again around Jan. 12 and we had several M-class flares. The transequatorial interconnecting loops continue to be interesting; we had two major regions, north and south, at almost the same heliolongitude. The regions are NOAA #'s 8439 and 8440, neither with very large spot area but extremely intense soft X-ray emission. Solar activity picked up later in the month; Five M-class flares occurred on the 14th and 15th as well as a large M5 LDE on Jan 20. Late in the month, solar activity again declined. The background dropped below the GOES C level though there were some very-short-duration flares, including an M flare. << Campaigns >> There were no formal joint observing campaigns, though we made some fixed-pointing PFIs to support TRACE observations. SOHO was temporarily offline during the reporting period. Page 2 << Science >> Eruption near disk center, 11-Jan-99 On 11-Jan we noted that an active region (AR 8431) just south of disk center had undergone substantial changes. It appears that an eruption occurred, and a GOES C-class flare was detected. Most notable was the bright S-shaped spine. At the eastern end of the bright spine, there was a sharply cusped loop. In the images made after 20:00 UT the faint plasma near the northern edge appears to expand further northward and to brighten. This can be observed in a movie of the event (http://www.lmsal.com/YPOP/ProjectionRoom/Weekly/990115.html). Using SXT images in the ALMG and AL12 filters, we have made maps of the plasma temperature for three times between 21:30 and 21:40 UT. The S-shaped spine is extremely hot (up tp 10 MK); the sharp eastern cusp particularly. These temperatures are taken after the initial rise-phase of the flare. The sharp cusp, and the loop expansion, are signatures associated with the ejection of mass. It is thought that the changes in the active region are due to a coronal mass ejection. Because of its location on the disk, a coronal mass ejection (CME) from this region at this time would very possibly be Earth-directed. Unfortunately, the LASCO instrument was offline at this time; LASCO has been extremely successful at detecting Earth-directed CME's, via the signature "halo". Cary Oler, keeper of the Solar Terrestrial Dispatch at the University of Lethbridge, notes that "the east and west ends of the filament that meandered through the region disappeared sometime between 16:00 and 20:00 UTC (based on H-alpha imagery)". We also received notice that a Type II radio event has been detected, very likely associated with this event. Preliminary analysis suggests that the shock responsible for this Type II burst was traveling at a speed of about 600 km/sec (1.3 million miles per hour). << Public Use of SXT Images >> We are continuing to make Yohkoh/SXT images available for a variety of uses. Efforts continue to make selected images available on the LMSAL SXT WWW homepage (http://www.lmsal.com/SXT/). We receive requests for the Yohkoh posters (#2 and #3) by way of the form on the SXT homepage. Currently we receive requests via our homepage at the rate of 2 or 3 per day. The WEB access statistics in January were 63412 accesses and 3075 Mbytes transferred. << Yohkoh Operations and Health >> Yohkoh and the SXT continue to function very well. SXT experienced a normal level of Single Event Upset (SEU) events during the month: SXT Bitmap error 10-January-99 Pass 1: 990110-1136 recovered in the same pass. Page 3 SXT Bitmap error 23-January-99 Pass 1: 990123-0722 recovered in the same pass. SXT Shutter error 30-January-99 Pass 4: 990130-0826 recovered in the next pass. SXT suffered another entrance filter failure on 30 Jan 1999. Efforts are currently underway to update the terminator images which allow us to correct SXT images for the increase in stray light. These corrections are well understood and we do not anticipate any long-term adverse affects from this failure. Page 4 << Data Flow >> Month Full Frame Images Observing Region Images Received Lost Received Lost Loss % QT FL Tot Thru Nov-96 420984 177702 1735309 379891 2115200 849269 28.58 Dec-96 7144 2643 25331 2087 27418 10412 27.52 Jan-97 7186 2747 21126 1257 22383 9915 30.70 Feb-97 6016 2034 22097 1072 23169 8961 27.89 Mar-97 7152 1300 26991 1209 28200 6394 18.48 Apr-97 6018 1055 23639 3890 27529 5349 16.27 May-97 7703 1455 29574 3783 33357 7121 17.59 Jun-97 7671 1557 25649 1396 27045 8045 22.93 Jul-97 8614 1385 32503 431 32934 6559 16.61 Aug-97 7316 987 23136 3519 26655 4990 15.77 Sep-97 7051 1479 33646 9596 43242 8887 17.05 Oct-97 7023 1134 26813 1827 28640 6043 17.42 Nov-97 6691 1376 26297 15306 41603 7131 14.63 Dec-97 6806 1013 28472 2136 30608 5263 14.67 Jan-98 5715 1803 23479 3232 26711 9918 27.08 Feb-98 6606 1644 25257 3606 28863 8989 23.75 Mar-98 6043 2056 23029 10399 33428 10939 24.66 Apr-98 6537 1103 22656 8087 30743 6339 17.09 May-98 7569 1838 28292 19018 47310 9868 17.26 Jun-98 6463 1638 24990 5618 30608 9051 22.82 Jul-98 6810 1892 27046 7357 34403 9970 22.47 Aug-98 5823 1960 22978 14126 37104 11167 23.13 Sep-98 6776 1432 21814 11626 33440 7753 18.82 Oct-98 6573 1901 23520 5198 28718 9220 24.30 Nov-98 6442 1695 25124 26948 52072 9920 16.00 Dec-98 5281 1839 19049 12469 31518 9488 23.14 Jan-99 362 6957 1309 826 2135 45194 95.49 Feb-99 937 309 7135 418 7553 2816 27.16 Mar-99 0 0 0 0 0 0 NaNQ Total 591312 225934 2376261 556328 2932589 1104971 27.37 Number of Full Frame Images Received: 591312 Number of Observing Region Images Received: 2932589 Total: 3523901 Approximate Number of Shutter Moves/CCD Readouts: 6134139 NOTES: * The loss of images is mainly due to BDR overwrites, but there are also occasional DSN dumps which are lost. * It is common to have observing regions which contain more than 64 lines, which requires multiple exposures to make a single observing region image. This is why the number of shutter moves is larger than the number of images received plus those lost. Page 5 << 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-96 53.08 846.2 171224 13860 22.9 N/A Jan-97 52.35 818.9 164785 11354 23.8 / 7 23.3 N/A Feb-97 51.95 803.9 159426 10346 21.1 N/A Mar-97 55.99 955.6 158428 12190 21.2 N/A Apr-97 53.14 848.4 176207 13265 20.8 N/A May-97 52.96 841.7 172052 13094 20.7 N/A Jun-97 53.71 869.8 182715 14910 19.8 N/A Jul-97 54.44 897.3 184518 20173 22.5 / 2 21.1 N/A Aug-97 54.06 883.1 188485 15549 20.1 N/A Sep-97 54.77 909.7 196501 17757 21.0 N/A Oct-97 54.85 912.8 198157 17857 21.5 N/A Nov-97 55.17 924.8 202153 18993 22.5 / 2 23.1 N/A Dec-97 55.51 937.6 206194 20219 21.9 N/A Jan-98 56.06 958.0 212189 22121 23.9 N/A Feb-98 55.94 953.7 209254 22122 23.8 / 2 22.6 N/A Mar-98 56.29 966.6 213519 23249 21.8 N/A Apr-98 56.44 972.1 214676 23890 20.8 N/A May-98 56.90 989.4 215651 26905 21.4 N/A Jun-98 57.11 997.5 216285 28223 20.1 N/A Jul-98 57.05 995.1 215628 27690 21.4 N/A Aug-98 57.36 1006.7 217355 29544 20.9 N/A Sep-98 57.43 1009.5 218520 29683 20.9 N/A Oct-98 57.59 1015.3 220504 30221 21.3 N/A Nov-98 58.17 1037.0 223755 34614 22.5 / 2 23.4 N/A Dec-98 57.84 1024.9 221880 32340 23.3 N/A Jan-99 N/A N/A N/A N/A 24.8 N/A Feb-99 58.73 1057.9 226631 37952 22.5 N/A Mar-99 N/A N/A N/A N/A 0.0 N/A NOTES: * The dark current calculations are using full half resolution 2.668 sec images not taken in during the SAA. The dark current rate assumes a "fat zero" of 30.5 DN and a gain of 100 e/DN. * The entrance filter failure of 13-Nov-92 eliminated the capability of taking optical images, so the optical transmission is not available after Nov-92. It also caused an increase in the dark current signal, however some of the increase shown here is an increase in the readout noise and is not a function of exposure duration. Page 6 << Personnel Travel >> SXT Foreign Travel between 1-JAN-99 and 31-JAN-99 HUDSON 1-JAN-99 * 22-JAN-99 22 29-JAN-99 31-JAN-99 * 3 (total of 25 days) MCKENZIE 4-JAN-99 31-JAN-99 * 28 (total of 28 days) SLATER 18-JAN-99 31-JAN-99 * 14 (total of 14 days) ---------------------------------------------------------------- Grand Total of 67 days for 3 people NOTE: The "*" signifies travel that actually ends after 31-JAN-99 SXT Foreign Travel between 1-FEB-99 and 28-FEB-99 ACTON 2-FEB-99 28-FEB-99 * 27 (total of 27 days) HUDSON 1-FEB-99 * 28-FEB-99 * 28 (total of 28 days) MCKENZIE 1-FEB-99 * 11-FEB-99 11 (total of 11 days) SLATER 1-FEB-99 * 18-FEB-99 18 (total of 18 days) ---------------------------------------------------------------- Grand Total of 84 days for 4 people NOTE: The "*" signifies travel that actually ends after 28-FEB-99 Respectfully submitted, Thomas R. Metcalf Frank M. Friedlaender Page 7 ======================================================================= Montana State University Activity Report for December 1998-January 1999 ======================================================================= (R. Canfield) INTRODUCTION The MSU group carried out SXT operations, data analysis, graduate and undergraduate research, and meeting organization. Piet Martens joined the SXT team as a Research Associate Professor in the Physics Department at MSU in January; we look forward to having Piet's considerable experience and expertise in SXT research and operations in the coming years. YOHKOH AND SXT OPERATIONS Weber spent December at ISAS, serving as SXT Chief Observer. McKenzie spent January at ISAS, serving as SXT Chief Observer. He also de-bugged some ``Quick Function Survey'' web page programs; this page (started by Hudson) allows a quick check of key instrument health diagnostics. Did some analysis of false flares during week 99_03; the Yohkoh machinery appears to be working well although we may want to adjust the RBM threshold for reducing HV. Canfield served as Mees Yohkoh Duty Scientist the last week of December. RESEARCH Acton concentrated on writing an improved de-streaking program for use in preparation of SXT composite images for the new movie. Amazing how hard it is to get a computer to recognize that the eye can see so easily. On a short visit to LMSAL in December he worked with Freeland and Metcalf on the new SXT movie. Canfield worked with Dave McKenzie and Hugh Hudson on sigmoidal structure and coronal eruptions using the Yohkoh SXT data for 1993 and 1997. Developed a critical argument on statistical significance and added it to the manuscript, which shows that both sigmoidal structure and sunspot area are independently related to the probability of eruption of a given active region, judged by signatures like arcades and cusps in the SXT data. Martens critically examined two recently published and related theories on the diamagnetic force as a source of the FIP effect in the solar corona, and gravitational damping of Alfven waves in coronal holes. Both papers consider collision-less effects in plasmas, much like in the paper by Fletcher and Martens on hard X-ray emission from loop tops (1998, ApJ, 505, 418). He found both contained fundamental errors, and is working on a publication to demonstrate this, and to present the correct solution. McKenzie worked on the SXT data for SOHO/TRACE JOP 80: maps of temp & EM, working on maps of sound speed & thermal energy content. Next he will associate the physical measurements with transient brightenings detected by Berghmans's automated procedure. He also worked on 13-nov-98 flare: morphology, maps of temp, EM, sound speed, thermal energy content, refining possible interpretation as chromospheric evaporation, rather than waves. He Page 8 continued period-search work in the SXT data with Dermott Mullan. He started analysis of M5.2 flare of 20-jan-99. This slow LDE is remarkable for a couple of reasons: an east-limb proton event with moving SXR footpoints, the flare-mode images catch both the brightening of the arcade and substantial motion of the loops. He and Hudson are examining the motion in this event to see if there's down-flow (like coronal rain or Simnett's ``backwards CME'') or possibly something else (like shrinkage). Weber worked on his differential rotation paper. As well, he began new research to understand apparent abrupt changes in the coronal rotation rates at mid-latitudes. Finally, he provided some time-series data to Peter Sturrock for a collaborative search for periodicities. SERVICE AND OUTREACH McKenzie patched some Weekly Science Nugget pages which had lost images or developed broken links over time. These are now linked to the YPOP pages and we've learned they are being used by teachers. Debugged a YPOP lesson page that was interfering with print commands in the new Netscape. Canfield revised a proposal for participant support for IAU Symposium 195, Highly Energetic Physical Processes and Mechanisms for Emission from Astrophysical Plasmas, MSU/Bozeman, 6-10 July 1999. He worked with Alexei Pevtsov on the American Geophysical Union book tentatively titled ``Magnetic Helicity in Space and Laboratory Plasmas''. All but one of the chapters of the book have now been submitted to the publisher. Canfield met with NASA Headquarters personnel to help organize a NASA Space Science Update on the sigmoids/eruptions result. The SSU is scheduled for March 9. He worked with McKenzie for a GRL color front cover related to the sigmoids/eruptions result. He set up two visits by graduate student applicants with solar research experience. He agreed to chair Andy Burnette's M.S. committee. He helped Peter Weiss at Science News with an article on laboratory plasma physics and its relevance to solar physics. He worked with MSU physics undergrad Angela Colman on CDROM production for MCCD/SXT flares. Papers Published: ``Energy and Momentum Deposition in Coronal Holes -- Solar Coronal Hole Simulations Compared with Interpretations of Yohkoh-SXT Observations'', K. Tziotziou, P.C.H. Martens, and A.G. Hearn, Astronomy & Astrophysics, 340, 203, 1998. Papers Accepted: ``Deriving Solar X-ray Irradiance from Yohkoh Observations'', Loren W. Acton, David C. Weston, and Marilyn E. Bruner, JGR-Space Physics, in press, 1999. ``Sigmoidal Morphology and Eruptive Solar Activity'', Richard C. Canfield, Hugh S. Hudson, and David E. McKenzie, Geophysics Research Letters, in press, 1999. Page 9 ``Helicity and Reconnection in the Solar Corona'', Richard C. Canfield and Alexei A. Pevtsov, in ``Magnetic Helicity in Space and Laboratory Plasmas'', eds. M.R. Brown, R.C. Canfield, & A. A. Pevtsov, Geophys. Monogr. Ser., AGU, Washington, D.C., in press, 1999. ``Helicity of the Photospheric Magnetic Field'', Alexei A. Pevtsov and Richard C. Canfield, in ``Magnetic Helicity in Space and Laboratory Plasmas'', eds. M.R. Brown, R.C. Canfield, & A. A. Pevtsov, Geophys. Monogr. Ser., AGU, Washington, D.C., in press, 1999. ``A Stable Filament Cavity with a Hot Core'', Hugh S. Hudson, Loren W. Acton, Karen L. Harvey, and David E. McKenzie, Astrophysical Journal Letters, in press, 1999. ``The Preflare Phase'', (invited) P.C.H. Martens, in the Encyclopedia of Astronomy and Astrophysics, D. Emerson and E.R. Priest (eds.), The Institute of Physics Publishing, in press, 1999. Talks Given: ``Search for Periodic X-ray Intensity Fluctuations'' David McKenzie, Solar Seminar, National Astronomical Observatory of Japan, Mitaka, Tokyo, Japan, January 22, 1999 ``Sigmoids and Coronal Eruptions: Helicity for Dummies'', Richard C. Canfield, Relativity/Astrophysics/Solar Physics Seminar, Montana State University, Nov 10, 1998. ============================================================= Univ of Hawaii Activity Report for December 1998-January 1999 ============================================================= (B. LaBonte) Our activities included support of Yohkoh operations and data analysis at ISAS, coordinated ground-based data acquisition (including designated Yohkoh campaigns) at Mees, collaborative analysis of Yohkoh/Mees data, and preparation of manuscripts. Operational support for SXT was provided by Nitta at Mees and LaBonte in Manoa. Our colleagues Mickey at Manoa, Canfield at Montana State University, Wuelser and Metcalf at Lockheed, and Hudson at Solar Physics Research Corporation aided in advice and oversight of Mees operations. Dr. Jing Li has officially joined the UH Solar Group. Jing worked with us in the past and has returned to work on SXT data analysis. She is currently combining Yohkoh SXT and SOHO UVCS data to map the variation of coronal temperature with height over closed and open field regions. Weather at Mees has been average for the winter season with our share of Page 10 storms. Changes in the Mees instrument status during this interval include: White Light Telescope down for a period with hardware problem, now fixed. Imaging Vector Magnetograph down for the upgrade of the CCD cameras, reassembled and test observations in progress. K-Line telescope removed from operation after hardware failure. Video images from the H-alpha coronagraph and H-alpha of the region of observation now available in quicklook form. LaBonte participated in the YOHKOH/SOHO/TRACE Coordinated Data Analysis Workshop in Palo Alto in November. IVM vector magnetogram movies of AR6227 were compared with the coronal images as a part of the effort to understand the coronal field geometry. Evidence was found that the loops most visible in the TRACE FeX images are those in contact with separatrix surfaces between flux systems and those connecting to rapidly evolving fields, in emerging flux regions. LaBonte presented a poster paper at the December AGU meeting on the evolution of the flare-productive region AR8210. This region arrived on the disk with a highly sheared but relatively simple form, with a single large spot. New flux emerging in the region appeared to come up directly under the existing spot and the region became more complex. The magnetic field vector showed a variety of secular and oscillatory changes in the azimuth and inclination as the new fields flowed around and out from the large spot. Mees observed several of the large flares and a complete analysis of the region is in progress. PAPERS PRESENTED Vector Magnetic Fields in New Cycle Regions. 1998. LaBonte, B. J.: EOS, V. 79, No. 45, p. F717 (December 1998 AGU) PAPERS USING MEES COORDINATED OBSERVATIONS: Canfield, R. C., and Reardon, K. 1998, Solar Phys., 182, 145. "The Eruptive Flare of 15 November 1991: Preflare Phenomena." Fisher, G. H., Longcope, D. W., Metcalf, T. R., and Pevtsov, A. A.: 1998, Astrophys. J., 508, 885. "Coronal Heating in Active Regions as a Function of Global Magnetic Variables." Pevtsov, A. A., and Longcope, D. W. 1998, Astrophys. J., 508, 908. "NOAA 7926: A Kinked Omega-loop?" Lee, J., White, S. W., Kundu, M. R., Mikic, A., and McClymont, A. N. 1999. Astrophys. J., 510, 413. "A Test for Coronal Magnetic Field Extrapolations" ============================================================ Stanford Univ Activity Report for December 1998-January 1999 ============================================================ (P. Sturrock, C. Roald, and R. Wolfson) Page 11 Colin Roald and Peter Sturrock are continuing their investigation of the coronal heating theory mentioned in the previous report, in which the key process is magnetic reconnection at the chromospheric level. Our model involves the emergence of magnetic bipoles within supergranulation cells, the migration of magnetic elements into the network, and "collisions" of elements of opposite polarity (leading to "cancellation") in the network. An analytical treatment shows that the coronal energy flux will vary approximately as a power law function of photospheric magnetic flux, the power law index decreasing from 2 for weak fields to 1 for strong fields. Roald has developed a numerical model of this process. At this stage, the model assumes a circularly symmetric supergranule, where magnetic elements are brought to the surface at some rate in the interior, then advected into the network by a combination of steady outflow and random diffusion. Since the model assumes that all emerged flux eventually collides with opposite-polarity flux, the heating rate is determined solely by the rate at which new flux is brought to the surface. The mean steady-state unsigned magnetic field is then controlled by the collision cross-section, which determines the mean lifetime of each element. With a small cross-section, the model produces a plausible quiet-corona heating flux of 10^{5.5} erg/cm^2/s with a mean field of 25 G; for larger cross-sections the same heating can be sustained with mean fields of 2 G or less. The relationship between the mean unsigned field computed here and the actual mean fields measured on the Sun is complicated. Further, it may not be reasonable to neglect the subduction as a process for removing elements without releasing energy into the corona; nor that, depending on geometry, some reconnections may occur as realignments, not cancellations. We are continuing our collaborative investigation with Sasha Kosovichev and Jesper Schou of the Stanford University SOHO/MDI team concerning the relationship between the soft X-ray luminosity of the solar corona and the photospheric magnetic flux. Mark Weber of MSU has generously provided us with a sequence of measurements of mean SXT flux over a region at disk center. Kosovichev and Schou will produce daily averages of the absolute value of the magnetic field for the same region for the same time interval, for comparison with the magnetic flux measurements. Roald and Wolfson will analyze the correlation. Sturrock will also perform a frequency analysis of the SXT data as a function of latitude, to search for evidence of "rigid rotation" that may be due to an internal process. Wolfson is examining Yohkoh SXT data from a region of the corona that was analyzed by Feldman et al. using the SUMER instrument. He finds that SXT shows an increase in coronal temperature with height, similar to that found by Wheatland, Sturrock, & Acton for another coronal region. In contrast, Feldman et al. concluded that the SUMER region was isothermal. They also found that the iron abundance declined more rapidly with height than did the abundance of neon, magnesium, and silicon--a decline they attributed tentatively to gravitational settling. To see whether the declining iron abundance might account for the discrepancy between SUMER and SXT temperature analyses, Wolfson is working with J. Lemen and P. Shirts at Lockheed to determine the Page 12 effect of a change in iron abundance on SXT temperature calculations. They find that, although iron contributes substantially to the flux in both SXT filters used in the analysis, the contribution is so similar in the two filters that removing iron altogether has only about a 12% effect on the calculated temperature. We are now considering the possibility that settling of other ions may be the reason for the SXT/SUMER discrepancy, and have developed new database files for the sxt temperature routines that account for differing elemental abundances. Sturrock has begun to investigate the time-scale for heavy ions to separate from the electron-proton background. A first estimate has been obtained by calculating the drift speed of ions in the known gravitational and electric field of a barometric proton-electron atmosphere. For Fe IX in normal coronal conditions, the drift speed is estimated to be of order 1 km/sec, leading to an estimate of the separation time of order one day. According to Sturrock's initial calculations, lighter ions should separate more rapidly. However, this result does not agree with the SUMER observations that indicate greater gravitational settling for iron than for neon, silicon and magnesium. We hope that further calculations will resolve this discrepancy. Article accepted for publication: Chromospheric Magnetic Reconnection and Its Possible Relationship to Coronal Heating, by P.A. Sturrock (Astrophysical Journal). =========================================================================== Solar Physics Research Corp. Activity Report for December 1998-January 1999 =========================================================================== (Karen L. Harvey and Hugh S. Hudson) KAREN L. HARVEY: Activities for December and January: (1) Continuing with writing up results of study with Hugh Hudson on the evolution of the magnetic field and coronal holes associated with the active region complex which occurred during several rotations in the summer 1996 to be submitted to a refereed journal. (2) Continued with analysis of data taken in collaboration with NSO/KP, Yohkoh/SXT, SOHO, TRACE, BBSO during observing program May 4-6, 1998 studying the behavior of magnetic flux in quiet sun canceling bipoles. The initial analysis is of a 12 hour time sequence of MDI magnetograms and TRACE images taken on early 4 May 1998. (3) Preparation of NSO/KP full-disk magnetograms and He I 10830 spectro- heliograms for SXT investigators for studies of the magnetic field and He I 10830 structures associated with X-ray structures. Planned Activities for February and March: Page 13 Continued analysis of (1) the magnetic fields and coronal holes related to the 1996 activity complex and the large scale field patterns with the objective of publication of the results in a referred journal. This includes determining using the SXT data how the coronal connections develop relative to the photospheric magnetic field evolution over the several month lifetime of this complex and the new cycle regions; (2) of the XBP data collected during several observing campaigns, concentrating on the more recent runs with the computer intensive reduction of the zonal scans (line profiles) in the Ca II 8542 and Fe I 8538 lines made during the 4-6 May and very successful 14-17 June 1998 runs and their relation to the XBP observed by SXT, (3) of filament channels related to coronal cavities, concentrating on the 1997 June-September observations and in 1993 February. PUBLICATIONS: Papers Accepted Hudson, H. S., Acton, L. W., Harvey, K. L., and McKenzie, D. E.: "A Stable Filament Cavity with a Hot Core", Ap. J. (Lett.) HUGH S. HUDSON During this period, H. Hudson's major research activities dealt with CMEs and the apparent observation by SXT of a coronal wave on May 6, 1998. This became the "science nugget" for Dec. 25, 1998, and then was presented as an ISAS seminar. Much material is available on the Web at http://www.solar.isas.ac.jp/sxt_co/981225.html and links therein. In brief, the phenomenon looks wave-like and matches the simultaneous EIT and ground-based meter-wave observations quite well. The occurrence of the wave observation gave us a chance to extend Jim Lemen's work on wave detectability, and we think we understand quite a bit better now how to observe more of these. Doing so is important because of the broad temperature coverage of SXT and its potential for seeing close-in at high cadence, the better to understand the launch process. H. Hudson served as Yohkoh tohban January 18-22 and as SXT chief observer on and off during December and January. Planned Activities for February and March: The initial paper on the May 6 wave has been drafted, and we intend to submit it promptly. There are many other papers waiting to be written! Which is to say that the present solar maximum is surprising us with many new discoveries and insights. Another hot topic is the development of large-scale loops interconnecting northern-hemisphere and southern-hemisphere active regions, or almost connecting them. In March there will be a Solar-B planning meeting in Tokyo, and a CDAW in Paris continuing the study of the 3-D CDAW held in Palo Alto last fall. Hudson intends to attend one or the other of these. Page 14 PUBLICATIONS: Papers Accepted Hudson, H. S., Acton, L. W., Harvey, K. L., and McKenzie, D. E.: "A Stable Filament Cavity with a Hot Core", Ap. J. (Lett.) (ftp://isass0.solar.isas.ac.jp/pub/hudson/nougat/985456.web.ps). Hudson, H. S.: "Coronal Mass Ejections at High Temperatures", Kiyosato meeting proceedings. Papers Published Hudson, H. S.: "Yohkoh and Non-Thermality in Flares", ISAS Cosmic Radiation Symposium 1998, p. 44 (ftp://isass0.solar.isas.ac.jp/pub/sxt_co/981016/981016_txt.html) Hardy, S. J., Melrose, D. B., and Hudson, H. S.: "Observational tests of a double loop model for solar flares," Proc. Ast. Soc. Australia 15, 318 (1998) =========================================================================== Naval Research Laboratory Activity Report for December 1998-January 1999 =========================================================================== (J. Lean) Magnetic Modulation of the Global Solar X-Ray Corona We are utilizing Yi-Ming Wang s potential field source surface(PFSS) model to quantify the influence of photospheric magnetism on global coronal heating variability throughout the solar cycle. The PFSS model extrapolates the photospheric magnetic field recorded in Carrington maps (made by NSO, WSO and MWO)into the corona, and estimates coronal brightness based on adopted parameterizations of heating in terms of magnetic field strength and geometry. Four such parameterizations are being considered in which coronal heating is proportional to 1) total loop field strength, 2) loop top field strength, 3) loop length and 4) field strength of loop s photospheric footprints. Integrating the calculated surface brightness over the full disk then provides a time series of global coronal flux that is directly comparable with the Yohkoh SXT fluxes. As well, the model constructs coronal brightness images that map the distribution of the brightness patterns, for comparison with the SXT images. We have now made these simulations daily throughout the solar cycle from Sept 1991 to mid 1998, in some cases using each of the magnetograms from the three different observatories. The highest correlation of the PFSS model with the SXT fluxes occurs when coronal heating is assumed to be proportional to the magnetic field of the total loop - in this case the correlation of the PFSS and SXT fluxes is 0.92. The assumption that coronal heating depends only on loop length is unable to replicate the global SXT flux changes throughout the solar cycle (correlation of 0.49). We are in the process of evaluating these initial results for the purpose of improving the PFSS model simulations, with guidance from a review of coronal heating theories, undertaken by Jim Klimchuk. Jim has reviewed 25 theories of coronal heating (many of them similar) to determine scaling laws relating the heating rate to physical parameters such Page 15 as field strength, loop length, pressure, and footpoint driver velocity. These scaling laws will be used to test the theories in two ways. First, they will be compared with the observational scaling law determined for Yohkoh SXT loops by Klimchuk & Porter (1995) and with a recent scaling law determined from photospheric magnetic field extrapolations by Klimchuk, Demoulin, and Mandrini. This latter work, also supported by this grant, is an extension of the Klimchuk and Porter study and involves many of the same active regions. Second, the theoretical scaling laws will be used to populate field lines with plasma in the global magnetic field models of Wang. Revised global PFSS models will then be compared with SXT data to determine which scaling law best reproduces the observations. This will hopefully yield new quantitative insights into mechanisms of coronal heating, on a wide range of spatial and temporal scales. John Mariska has completed determining the daily "basal" flux level in the Yohkoh BCS S XV channel for comparison with the nonflaring SXT fluxes determined by Acton and for comparison with other measures of solar activity, such as the 10.7 cm flux and the GOES fluxes. Initial examination of the S XV data suggests that the measurements went down to a background level near solar min and thus that not all the time series may be useful. =========================================================================== University of New Hampshire Activity Report for December 1998-January 1999 =========================================================================== (T. Forbes) A movie has been completed which shows the evolution of magnetic field and plasma temperature in a model of X-ray flare loops. The model incorporates both magnetic reconnection and chromospheric evaporation, and is able to account for both the apparent motion and temperature evolution of flare loops during the gradual phase of two-ribbon flares. During the gradual phase the hottest loops lie above cooler loops. However, the movie also shows that the model predicts the hottest loops to lie below cool loops during a very short interval after flare onset. The reversal in the relative position of hot loops and cool loops occurs because there are two competing processes, namely heating by magnetic reconnection and cooling by radiation and conduction. In the absence of any cooling, the reconnection of the strong magnetic fields at the base of the corona, and the weaker magnetic fields higher up, leads to a temperature gradient which decreases with altitude. Cooling by radiation and conduction can reverse the gradient because field lines which lie far below the reconnection site have undergone considerable cooling. The movie shows that by the time the flare loops are well formed (when Yohkoh typically observes them), the hottest loops always lie at higher altitude than the cool loops. Page 16 =========================================================================== University of California Activity Report for December 1998-January 1999 =========================================================================== (G. Fisher) Berkeley personnel involved with Yohkoh research over the past 2 months include George Fisher, D. Tod Woods, Neil W. Griffiths, and Chris Johns-Krull. Fisher has been working with Woods and Griffiths on the analysis of overlapping SXT and SUMER data for a small unnamed active active region along the central meridian, observed on 19-APR-1997. The combination of density diagnostics from the OIV 1399,1401 lines, and differential emission measures determined from strong O and N transition region lines observed by SUMER, in conjunction with the SXT data, should allow us to to characterize the differential emission measure distribution, density distribution, and ``filling factor'' for the emitting material in this small active region. Loren Acton of Montana State University has provided us with the reduced SXT images for the active region. Fisher is continuing his work on comparing relationships between the magnetic field in active regions, as measured with the Haleakala Stokes Polarimeter, with coronal heating determined from X-ray radiances, measured with SXT. Fisher and Metcalf (of Lockheed ATC) have succeeded in modifying the existing data analysis software to interactively correct poor vector magnetogram positions which are recorded in the magnetogram database. These corrections will allow a much greater fraction of the combined data to be used in the study (previously, magnetograms with incorrect positions on the disk were rejected from the study). In addition, Metcalf and Fisher have now extracted about half of the SXT data from the jukebox system at Lockheed onto disk to facilitate a more rapid analysis of the combined SXT and vector magnetogram data. The solar group at UCB has just acquired sufficient disk space that all the relevant SFD data necessary for the study can now be stored online simultaneously without having to extract data from tape. Fisher and Chris Johns-Krull (also at SSL/UCB) plan to travel to Big Bear Solar Observatory (BBSO) in early March to test a new experimental setup to measure linear polarization in Halpha during solar flares. It has been proposed that strong center-to-limb linear polarization may be produced by proton beams during solar flares; the experiment is an attempt to look for such a signature. They succeeded in calibrating and testing the system during their trip to BBSO in October, but no flares were observed during the week. They hope to coordinate their observations with HXT and with the Mees Solar Observatory at UH. 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 February 1999 January 1999 |------------------------------- | 6. PERFORMING ORG | CODE: O/H1-12 -----------------------------------------------|------------------------------- 7. AUTHOR(S) | 8. PERFORMING ORGANIZA- T. R. Metcalf | TION REPORT NO: F. M. Friedlaender | |------------------------------- -----------------------------------------------|10. WORK UNIT NO. 9. PERFORMING ORGANIZATION NAME AND ADDRESS | Lockheed Martin Missiles and Space |------------------------------- Advanced Technology Center, O/H1-12, B/252 |11. CONTRACT OR GRANT NO. 3251 Hanover Street, Palo Alto Ca. 94304 | NAS8 - 40801 -----------------------------------------------|------------------------------- 12. SPONSORING AGENCY NAME AND ADDRESS |13. TYPE OF REPORT AND Marshall Space Flight Center (Explorer Program)| PERIOD COVERED Huntsville Alabama 35812 | Progress report for the month Contact: Larry Hill | of January 1999 |------------------------------- |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