Page 1 PROGRESS REPORT THE SOLAR-A SOFT X-RAY TELESCOPE (SXT) PROGRAM (CONTRACT NAS8-40801) (for July 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 All of the programmatic and financial aspects of the program are continuing in a nominal manner. We are all dismayed that a House Appropriations Committee panel imposed a very serious reduction in the budget for space science programs. SOLAR ACTIVITY In early July, activity continued to be moderately high, with many C flares, several M flares, but still no X flares, supporting the Hudson heuristic: "Big flares only occur in the rising and declining phases of solar activity." This level of activity was not to hold, though, and by mid-month the GOES database showed baseline activity approaching solar minimum levels. The sun still produced numerous interesting events, including an M-class flare co-observed with TRACE, transequatorial loops, a giant polar crown filament near the south pole and the birth of a CME off the west limb. Yohkoh observed one M-class flare that was simultaneously observed by TRACE. The HXT data shows a very soft spectrum for this flare, strange for such a strong event. Observations detected a new spot group at N42. This region formed a minor "belt" with two unspotted bipolar regions at the same latitude. It is unusual to have more than one active region visible at such a high latitude. One region is the return of old Region 8585 that was remarkable for its eastward drift of 1-degree per day for the previous two solar rotations. The slow rate of rotation at this latitude (29.7 days synodic) moves these regions eastward relative to the rest of the active regions and filament channels. The encounter between this region and the regions at lower latitudes may force rearrangements in the overlying coronal structures and trigger CMEs. (from "Solar Status Report", P. McIntosh). Page 2 SXT observed the beginnings of a large CME blowing off the W limb on 15-July, later evident in LASCO C2 and C3 movies. In late July SXT observed high solar activity but no X-class flares. There were 9 M-class events from 4+ regions, including the beauty on 25-July that's the subject of a science nugget. CAMPAIGNS This was a quiet period from a campaign standpoint, with no active campaigns taking place. The serendipitous flare observation with TRACE is the only recorded activity during this time. SCIENCE Fletcher worked with Martin Hendry, from Glasgow University, on a technique (developed in the field of galactic dynamics) to determine which of a set of particle orbits are chaotic. The technique utilizes Lyapunov exponents, the integral of which over time is a measure of the divergence of neighboring orbits. They plan to apply this to the case of particle acceleration in X-type neutral points in the presence of oscillating EM fields. The method should enable them to determine which regions of phase space lead to chaotic orbits, which in turn lead to rapid particle acceleration. Acton worked on a program to convert SXT data to solar irradiance in specified bandpasses. The program incorporates 2-filter coronal temperature measurements (full disk) for use in deriving the radiance. The program will be further improved by taking the temperature only from the portion of the images below 1.1 solar radii. This will greatly improve the signal to noise ratio over the full-image technique used up to now. Preliminary results for several weeks of interest have been sent to Ahilleas Maurellis in Holland for use in computing fluorescence radiation from the Jovian atmosphere. Canfield worked with summer undergrad Tom Bethell on recasting the SXT chief observer weekly reports into nuggets more suitable for outreach. The nuggets are nearly complete and can be viewed at http://solar.physics.montana.edu/nuggets. 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 July were 74395 accesses and 3539 Mbytes transferred. YOHKOH OPERATIONS AND HEALTH Yohkoh and the SXT continue to function very well. Page 3 SXT experienced a normal level of Single Event Upset (SEU) events during the month: SXT BITMAP Error 05-July-99 Pass 1: 990705-0412 Recovered in Pass 1 SXT BITMAP Error 26-July-99 Pass 4:990726-0102 Recovered in Pass 4 Page 4 DATA FLOW Month Full Frame Images Observing Region Images Received Lost Received Lost Loss % QT FL Tot Thru May-97 462203 188936 1884067 393189 2277256 897421 28.10 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 5962 2005 21490 15770 37260 10561 22.08 Jan-99 5494 1825 20087 17620 37707 9622 20.33 Feb-99 5729 1525 30802 9798 40600 10630 20.75 Mar-99 6807 1844 24721 12354 37075 10064 21.35 Apr-99 6715 1371 25113 4179 29292 7791 21.01 May-99 3330 1053 24258 8006 32264 9995 23.65 Jun-99 0 0 0 0 0 0 -NaN Jul-99 0 0 0 0 0 0 -NaN Total 618769 226452 2495239 610342 3105581 1106136 26.26 Number of Full Frame Images Received: 618769 Number of Observing Region Images Received: 3105581 Total: 3724350 Approximate Number of Shutter Moves/CCD Readouts: 6395695 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 (%) 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 57.01 993.7 215499 27493 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 57.86 1025.5 221918 32420 23.8 N/A Jan-99 58.74 1058.6 227503 38238 23.1 N/A Feb-99 58.44 1047.4 224002 36198 23.2 N/A Mar-99 59.26 1078.1 227900 43051 21.7 N/A Apr-99 58.82 1061.4 225973 38963 23.8 / 1 21.4 N/A May-99 58.68 1056.4 225385 37726 22.5 N/A Jun-99 59.40 1083.0 230091 42440 0.0 N/A Jul-99 60.04 1107.2 232187 48542 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-JUL-99 and 31-JUL-99 HANDY 1-JUL-99 * 31-JUL-99 31 (total of 31 days) HUDSON 1-JUL-99 * 31-JUL-99 * 31 (total of 31 days) MARTENS 1-JUL-99 * 2-JUL-99 2 (total of 2 days) SHIRTS 15-JUL-99 31-JUL-99 * 17 (total of 17 days) SLATER 1-JUL-99 * 2-JUL-99 2 (total of 2 days) ---------------------------------------------------------------- Grand Total of 83 days for 5 people NOTE: The "*" signifies travel that actually ends after 31-JUL-99 SXT Foreign Travel between 1-AUG-99 and 31-AUG-99 HUDSON 1-AUG-99 * 22-AUG-99 22 30-AUG-99 31-AUG-99 * 2 (total of 24 days) NITTA 28-AUG-99 31-AUG-99 * 4 (total of 4 days) SHIRTS 1-AUG-99 * 15-AUG-99 15 (total of 15 days) ---------------------------------------------------------------- Grand Total of 43 days for 3 people NOTE: The "*" signifies travel that actually ends after 31-AUG-99 Respectfully submitted, Thomas R. Metcalf Frank M. Friedlaender Page 7 7 ======================================================================= Montana State University Activity Report for June 1999-July 1999 ======================================================================= (A. Davey) CONFERENCES A number of the member of the Solar Group attended the AAS/SPD meeting in Chicago. Canfield organized and chaired a special session at the Chicago AAS/SPD meeting "Here Comes the Sun: Plans for the Y2K Solar Maximum", which included a paper reviewing the accomplishments of Yohkoh, by Markus Aschwanden. Presentations were also made by Martens, Elizabeth Noonan and Kankelborg. At the beginning of July, MSU hosted IAU195 - Highly Energetic Physics Processes and Mechanisms for Emissions from Astrophysical Plasmas for which Loren Acton was co-chairman of the Local Organizing Committee. Piet Martens will help edit the proceedings. Most of the members of the MSU Solar Group attended and helped in the organization in one form or another. Longcope and Martens gave talks. SCIENCE ------- During June, Acton concentrated on developing a reliable way to make second-order correction for stray light in composite FFIs. which he describes as "Tough business". Schemes that work beautifully for solar min conditions fail badly for high activity conditions. He reports as not having given up hope on this...yet ! Ahilleas Maurellis at the FOM-Institute for Atomic and Molecular Physics in Amsterdam is working on modeling X-ray emission from Jupiter and needed the solar x-ray input. Acton wrote sxl2irradiance.pro, a program that converts SXT full-disk fluxes to radiance in a spectral band. It makes use of 2-filter color temperatures for a spectral distribution. This feature greatly increases the accuracy of the result according to Acton, Weston and Bruner (see publications). Further work will involve taking the temperature only from the portion of the images below 1.1 solar radii. This will greatly improve the signal to noise ratio over the full-image technique Acton has been using. During June and July, Canfield worked with summer undergrad Tom Bethell on recasting the SXT chief observer weekly reports into nuggets more suitable for outreach. The results of this work may be viewed at (http://solar.physics.montana.edu/nuggets/index.html). Canfield also worked with MSU undergrad Zachary Blehm to identify the time and site of all Yohkoh cusps and jets on the SXT video disk, starting with 1993 and with Hudson and Gibson to define a Max Millennium sigmoids observing program, in which Yohkoh will play a central role. Page 8 This summer we are again joined by participants in the Montana Apprenticeship Program for Native American high school students. Canfield, Pevtsov and David McKenzie worked with two students to enlarge the database of sigmoids and eruptive active regions. During June and July, McKenzie continued work on the observations of flow fields above LDE flare arcades. He compared SXT images to coincident (spatial and temporal) MLSO H-alpha images, and found no evidence for H-alpha blobs in the region above the arcades where X-ray voids are observed. Examination of EIT & TRACE images yields same result: EUV sees the arcade, but doesn't seem to reveal anything above the arcade. A comparison of the measured down flow velocities and the times/locations of the velocity measurements may place some constraints on the necessary rise speed of the CME material, if the down flow is purely gravitationally motivated; However McKenzie does not think that it is likely this will pan out as a useful constraint for determining the force which accelerates the X-ray voids. With Davey, McKenzie fixed some bugs in SXT_OBSRPT and added an HTML interface to give the whole solar community access to the observing logs, with the aim enabling wider use of the archival data. During his tour of duty at ISAS in June, Martens spent some time putting together an SXT campaign catalog on-line for the period 1996-1999. (http://isass1.solar.isas.ac.jp/sxt_co/sxt_catalog.html) He also updated the SXT_CO handbook (including some tips for novices !). Handy spent July at ISAS and while not acting as Chief observer passed the time delving into flares co-observed by TRACE and Yohkoh, and found that number to be alarmingly low. There are several databases that hard-working folks have put together, but the results are erroneously high with many false positives in these datasets ! The aim of examining co-observed flares was to see how HXT and TRACE UV interrelate. Handy also attended the Nobeyama CDAW during which time the sun smiled upon the assembly and blurted out an M-class flare (July 25) that was well observed by Yohkoh. A blitzkrieg of data analysis followed, and more work is to come. Another success was to ignite a fire storm under the TRACE team to get a real concerted flare program going, in a quest to unify TRACE and Yohkoh. The small FOV of TRACE and Yohkoh S/C night though, makes this really hard. OUTREACH and SERVICE Canfield, Martens and Pevtsov performed various refereeing duties. Canfield Participated in a press conference and seminar for science writers entitled "The Coming Sunspot Maximum". MSU Solar Physics again participated in the Montana Apprenticeship Program for Native American high school students. (See science). While at the Nobeyama CDAW Handy took the opportunity to do some TRACE evangelization! Page 9 Kankelborg contributed two TRACE images; a full-disk mosaic and an active region image, to an astronomy guidebook called "Montana Skies" that will hopefully be published in 2001. McKenzie participated in a Star Party weekend at Yellowstone, sponsored by the Museum of the Rockies. PUBLICATIONS Talks: Canfield: "The Max Millennium Program in 1999/2000", Invited paper, 194th AAS meeting, Chicago, June 2, 1999. Kankelborg: "VLA Decimetric Observations of EUV Transient Events Detected by SOHO and TRACE", by R. F. Willson and C. C. Kankelborg, was presented by Willson at the SOHO 8 Workshop, 22-25 June 1999, Paris, France. Papers published: "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, Wahington, D.C., 111, 197 "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, Wahington, D.C., 111, 103. "Deriving solar X ray irradiance from Yohkoh observations", Acton, L. W., Weston, D. C. and Bruner, M. E., J. Geophys. Res., vol. 104, pp. 14,827-14,832 (1999). Fisher G. H., Longcope D. W., Linton M. G., Fan Y., and Pevtsov A. A.:1999, ``The Origin and Role of Twist in Active Regions'', in Stellar Dynamos: Nonlinearity and Chaotic Flows, ed. M. Nunez, A. Ferriz-Mas, P.A.S.P. Conference Series, Vol. 178, 35-42. Papers Accepted: "Coronal Heating by Resonant Absorption: the Effects of Chromospheric Coupling", by A.J.C. Belien, P.C.H. Martens, and R. Keppens, has been accepted by ApJ. "The Nature of Moss", by P.C.H. Martens, C.C. Kankelborg, and T. Berger, was submitted to ApJ and accepted on condition of some updates and clarifications. Pevtsov A. A., and Latushko S. M.: 1999, "Current Helicity of Large-Scale Photospheric Magnetic Field", Astrophysical Journal, accepted Page 10 Books published: "Magnetic Helicity in Space and Laboratory Plasmas", Michael R. Brown, Richard C. Canfield and Alexei A. Pevtsov, editors, American Geophysical Union, Geophysical Monograph Series, vol. 111. OPERATIONS Canfield served the last two days of June as Yohkoh Duty Scientist at Mees. Worked with Dale Gary (OVRO/NJIT) and Neal Ranns (SOHO/MSSL) to organize the first Max Millennium campaign, to which Yohkoh made a strong observing commitment. Martens spent the most of June at ISAS as SXT Chief Observer, collaborating with Hugh Hudson. In this period a streamer campaign between SXT and UVCS was held, the first Max Millennium flare campaign carried on for a fortnight, and SXT supported the SERTS rocket underflight. Handy spent July at ISAS as SXT Chief Observer. COMPUTING MSU took delivery of a new server. This server provides 300 Gig of storage for work on the new SXT movie. Some space has also been given over to hosting more of the TRACE database. The new machine is called SXT4 ! ============================================================= Univ of Hawaii Activity Report for June 1999-July 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 and Li in Manoa. Our colleagues Kupke and 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. Weather at Mees was good during this interval, with observations obtained on 85% of all possible days. Minor problems with the Imaging Vector Magnetograph, the White Light Telescope and Imaging Spectrograph occurred and were fixed; a problem with the Stokes Polarimeter is under repair. Mees supported the Max Millennium Observing Campaign #1 during the last 2 weeks of June. LaBonte spent 4 weeks at LMSAL in June/July, working on comparisons of Mees Page 11 H-alpha imaging spectra and vector magnetograms with data from TRACE, SOHO, and YOHKOH. Li spent 3 days at Goddard Space Flight Center during the joint YOHKOH/SOHO/TRACE campaign to observe the corona above an active region in early June. Good data was obtained with all instruments and Jing has begun gathering the datasets and calibration files to perform the science analysis. Li has completed her study of the background solar corona during the time of activity minimum in 1996. Using time series of coronal images, she was able to separate the background corona from the short term effects of active regions. Special attention was paid to the polar coronal holes, where Li found a systematic variation of emission with latitude. Li was able to construct a model of coronal density as a function of latitude and height that fits the observations inside and outside the polar holes more accurately than previous global coronal models. This work is being prepared for publication. ============================================================ Stanford Univ Activity Report for June 1999-July 1999 ============================================================ (P. A. Sturrock) Michael Wheatland visited Stanford University for the month of July. He and Peter Sturrock reviewed the method for reconstructing force-free magnetic fields by means of an optimization function, originally proposed by George Roumeliotis when he was at Stanford. Wheatland developed a code based on this concept and applied it to a known model (the Low--Lou model) of a 3-D force-free field. When we use the known values of the vector magnetic field on all six of the bounding surfaces of a rectangular cell, and use 30 x 30 x 20 grid points, the code can be run on a workstation and converges reasonably rapidly. The method produced a reconstructed field that is a good fit to the model. An article on this work is being prepared. The important next step is to find a way to implement this scheme when the boundary conditions on the side and upper boundaries are not known. We are exploring the simple expedient of selecting functions W_1 and W_2 that are small or zero on the ``remote'' surfaces. Another possibility is that we add to the above volume integral a weighted surface integral of B^2, so that the method finds the solution that is a good fit to the photospheric conditions and falls off most rapidly towards the remote surfaces. Colin Roald and Peter Sturrock are continuing their investigation of the coronal heating theory mentioned in previous reports, 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. Sturrock, Roald and Wolfson have submitted an article describing an analytical model of the magnetic-element kinetics in which elements arise only within the Page 12 supergranulation cells and annihilate only in the network regions. This leads to a simple analytical relationship between the mean coronal energy flux density and the mean photospheric magnetic flux density. In the limit of weak fields, the relationship is quadratic, going over to linear in the strong-field limit. Roald has continued his investigations of a more complete version of this model, which includes diffusion and in which collisions can occur anywhere. He has written a time-dependent code and tried to push the model towards the limit of low diffusivity; unfortunately the equations become numerically intractable in this limit. A paper describing the results is in preparation. Sturrock and Roald remain interested in spectrum analysis of the SXT data set, kindly provided by Mark Weber of Montana State University, giving daily average values of the SXT flux as described in previous reports. Spectrum analysis of this data set has yielded a surprising split in frequencies, with low to mid-latitudes appearing to rotate rigidly at 13.5 yr^-1 while higher latitudes rotate at 12.9 yr^-1. The simplest explanation is that the coronal signal may be dominated at low and mid-latitudes by fields emerging from particular locations in the photosphere, which would thus impart a single characteristic frequency. We have begun frequency analysis of magnetogram data to investigate this possibility. Publications ------------ Sturrock, Roald, and Wolfson, 1999, "Chromospheric magnetic reconnection and its implication for coronal heating", ApJ, submitted Wolfson, Roald, Sturrock and Weber, 1999, "Coronal X-ray Brightness and Photospheric Magnetic Field: A Study in Correlations," ApJ, pending Wolfson, Roald, Sturrock, Lemen and Shirts, 1999, "Temperature structure of the quiet corona: an SXT-SUMER discrepancy", ApJ, pending =========================================================================== Solar Physics Research Corp. Activity Report for June 1999-July 1999 =========================================================================== (K. Harvey and H. Hudson) KAREN L. HARVEY: Activities for June and July: (1) Continued with analysis of data taken in collaboration with NSO/KP, Yohkoh/SXT, SOHO, TRACE, BBSO during three observing campaigns: 18-23 September 1997, 4-6 May 1998, and 14-16 June 1998 to investigate the behavior of magnetic flux in canceling bipoles in the quiet sun canceling bipoles. The reduction of the simultaneous measurements of the magnetic and velocity fields, line depth and equivalent width at two levels of the Page 13 solar atmosphere: in the chromosphere (Ca II 8542) and photosphere (Fe I 8538). The data are being analyzed to determine if magnetic flux in canceling bipoles in the quiet sun is submerging below the photosphere or emerging into the solar atmosphere. Intensity images from the SXT, TRACE and SOHO in several X-ray and EUV lines are being compared to deduce the height structure of the associated coronal bright points. The advantage of the NSO/KP magnetic flux measurements is the precise co-alignment of magnetic, velocity and intensity structures at two levels of the atmosphere separated by about 600-800 km. The comparison of the chromospheric and photospheric shows interesting spatial differences: the magnetic network in the chromospheric covers a larger area than in the photosphere due to the spreading or divergence of the field with height. This divergence, however, is not symmetric about the photospheric network element. In addition, in a few network elements, the chromospheric structure is spatially displaced from the corresponding photospheric structure. It will be interesting to see if the coronal field reflects the apparent non-radial magnetic configuration in such features. Ascertaining if magnetic flux is submerging in canceling bipoles is being based on whether the magnetic flux and timing of the flux disappearance differs between the chromosphere and photosphere. The reliability of this observation depends on the noise in the magnetograms, which for these data sets is higher than in the normal synoptic magnetograms. At this time, we are trying to determine the noise characteristics of the data. (2) Updating the publication list of Yohkoh papers published, accepted, and submitted to refereed journals. (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 August and September: Continued analysis of (1) of the XBP data collected during several observing campaigns, concentrating on the more recent runs. (2) the magnetic fields and coronal holes related to the 1996 activity complex and the large scale field patterns. This includes determining from 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. HUGH S. HUDSON Activities for June and July: Worked with Brian Handy on HXT/TRACE comparisons; worked with Joe Khan on interconnecting loops. As usual, did some interface work for Mitsuru Soma's ephemeris calculations for the August 11 eclipse; the new wrinkle this time is that he has done predictions for TRACE as well as Yohkoh. These can be seen on the science nugget for July 16, which I Page 14 hope to maintain as the ephemeris changes. There has been some e-mail discussion with the Wroclaw group about the use of the Yohkoh data from this eclipse for assessment of the SXT point-response function, so we will try to set up full-resolution observations on a bright region that will be occulted in an appropriate way. Completed a "Perspective" for Science magazine, co-authored by T. Kosugi and reviewing coronal heating. This will be published in the August 8 issue along with the paper by Nakariakov et al. that inspired the interest. Planned activities for August and September: 1. Act as SXT_CO during August, including Whole Sun Month observations and the August 11 eclipse. 2. Continue (finish?) work on the May 6, 1998 wave, and look for more. 3. Extend the analysis of trans-equatorial loops and present it as a part of my paper on large-scale structure at the Monterey meeting (late August). PUBLICATIONS: Papers Accepted H. S. Hudson and T. Kosugi, "How the Sun's Atmosphere gets Really Hot," Science (August 8 issue). Papers Published D. E. McKenzie and H. S. Hudson, "Observations of Motions and Structure above a Solar Flare Arcade," ApJ 519, L93 (1999). D. M. Zarro, A. C. Sterling, B. J. Thompson, H. S. Hudson, and N. Nitta, "SOHO EIT Observations of Extreme-Ultraviolet `Dimming' Associated with a Halo Coronal Mass Ejection," ApJ 520, L139 (1999). =========================================================================== Naval Research Laboratory Activity Report for June 1999-July 1999 =========================================================================== (J. Lean) Magnetic Modulation of the Global Solar X-Ray Corona During the past two months Klimchuk completed the draft of his paper entitled "Magnetic Field and Plasma Scaling Laws: Their Implications for Coronal Heating Models". Klimchuk and coauthors identified more than 20 coronal heating models, and determined for each how the heating rate depends on the strength of the coronal magnetic field, the length of the field line, the plasma density, and the footpoint velocity (where relevant). Page 15 They also determined from extrapolations of photospheric magnetograms that B ~ L^(-0.9) for the range of lengths corresponding to active region loops observed by SXT. Combining this with earlier results (Klimchuk and Porter, 1995, Nature, 377, 131), they were able to conclude that DC coronal heating models are in generally better agreement with observations than are AC (wave) heating models. Mariska began working with SNOE scientists (SNOE, launched last year, also measures X-ray fluxes) and is also extending and upgrading NRL's physics-based EUV emission measure variability model to cover wavelengths below 10 nm, in the Yohkoh SXT band. The goal is an improved prescription of the spectral dependence of the flux variability within the Yohkoh passband, leading to a better flux time series for the solar cycle. Wang and Lean began utilizing ground-based magnetograms to simulate coronal variability on multi-decadal time scales, i.e., during the past three solar cycles, based on the potential field modeling of the SXT fluxes (presented at the SPD). We plan to extend and update this approach by incorporating the results of Klimchuk's broad study (above) into Wang's model and use the SXT images and fluxes to help arbitrate among the various scaling laws. =========================================================================== University of New Hampshire Activity Report for June 1999-July 1999 =========================================================================== (T. Forbes) Forbes continues to work on a model for the heating of flare loops by magnetic reconnection. At the moment this work involves a lot of detailed mathematical development. ======================================================================= University Of California Activity Report for June 1999-July 1999 ======================================================================= (G. Fisher) Berkeley personnel involved with Yohkoh research over the past 2 months include George Fisher, D. Tod Woods, Neil W. Griffiths, Chris Johns-Krull, and Jim McTiernan. Fisher and Metcalf (LMSAL) have worked on code to compute power spectra for the electric current computed from vector magnetograms taken with the Haleakala Stokes Polarimeter at Mees Solar Observatory, to correlate with the X-ray luminosity in active regions. Most of their effort has been spent on testing the reliability of the code with simulated current data, to make sure the power spectra correctly account for projection effects and the phase space corrections in 2D. Once the code checks out completely, they will then compute the power spectrum of their large database of active regions, and compare with X-ray radiances of active regions measured with SXT. Page 16 ------------------------------------------------------------------------------- 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 August 1999 July 1999 |------------------------------- | 6. PERFORMING ORG | CODE: O/L9-41 -----------------------------------------------|------------------------------- 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/L9-41, 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 July 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 | 16 | ------------------------|------------------------|-----------------|----------- For sale by: Superintendent of Documents, U.S. Government Printing Office