Page 1 PROGRESS REPORT THE SOLAR-A SOFT X-RAY TELESCOPE (SXT) PROGRAM (CONTRACT NAS8-40801) (for May 1998) 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 Although some progress is being made on the definitization of the operational amendment for 1998, it did not get completed this month; MSFC is hoping to complete this by mid-June. The Co-I's, however, are continuing their support and we are maintaining a strong technical presence in all areas. << Solar Activity >> In the first half of May, Yohkoh observed many flare triggers and made some splendid observations. The many flares were accompanied by a correspondingly large number of CMEs; we seem to find that flares with clearly defined soft X-ray eruptive structures are more common than they had been in the last cycle. There were many other items of real scientific interest, including a remarkable set of transequatorial interconnecting structures that participated in the ejective flare and CME of May 3. In mid-May, solar activity was moderate, with three M flares, and was clearly reduced in comparison with the previous weeks. The huge filament complex in the S rotated beyond the W limb, and, as of May 16, had defied all predictions and not erupted In late May, solar activity was low, with only a few C flares. By the end of the month, the GOES background was near the B level. SXT observed an LDE on May 31. We have now identified the origin of this event to have been not in one of the W limb regions, but on the SE instead. << Campaigns >> May was a busy month with SXT participation in a number of campaigns. Page 2 In early May, observational work centered on the XBP campaign (JOP 082), and upon observations for JOP 059 and test exposures for JOP 080, which are concerned with signatures of coronal heating (JOP 059) and coronal and transition region dynamics (JOP 080), respectively. These JOPs are SOHO campaigns, led respectively by Robert Walsh (St. Andrews) and Frederic Clette (Royal Observatory of Belgium). SXT supported XBP studies led by Karen Harvey, with participation from SOHO and TRACE. These observations were poor, by our standards, because activity was at such a high level that scattered-light background made them less sensitive than usual. Bright points were detected, but not so many. SXT took part in SOHO JOP 080, making fast-cadence PFIs of an active region. This JOP was designed to take advantage of EIT's shutterless-operation mode, in which EIT can make images at a higher-than-normal cadence (16 seconds). Instruments taking part in the JOP included SXT, EIT, TRACE, MDI, CDS, SUMER, HAO, and La Palma. SXT also took part in SOHO JOP 059, making PFIs of a number of active regions to support CDS study. During the week 11-May-98 to 18-May-98, SXT took part in two Joint Observing Programs (JOPs). Both of these emphasized microflares and time-series analysis. Things worked very well for SXT in that we got the (fixed) exposures right, and also put the FOV exactly where and when the other spacecraft were observing. A good experience all around from the operations point of view, and the data look extremely good: some nice examples of loop-filling flows, for example, which will be extremely interesting to see with low-temperature data from TRACE and SOHO; also there were tiny "three-legged flares" on the Nobeyama model. During the week 18-May-98 to 24-May-98, SXT observations supported JOP 075, and also CDS and TRACE measurements of a prominence on the northwest limb. On two evenings we looked for jets with special PFI tables, but with very little success. Finally, SXT supported AR studies led by Karin Muglach, with participation from SOHO and TRACE. For the latter, this is part of a two-week "staring" observation on a single active region, AR 8227 (central meridian passage on approximately May 31). This series of observations has led (May 30) to some active-region jets well-observed by SXT. We've made numerous efforts to observe jets in this manner, normally unsuccessful, so this is quite nice. We expect that the TRACE data on these jets will be beautiful! << Science >> This month's science focused on the SPD/AGU meeting at the end of May. There were many posters and talks which included Yohkoh data and analysis. Nitta continued to characterize the loop top source of flares, especially in terms of its spatial relationship as seen in SXT Be filter and HXT L-band images. He compared the centroids under various criteria such as above NN % of the peak and the first XX brightest pixels, and checked how solid the Page 3 conclusions were that he had reached a few months before. Part of the result was presented as a poster at AGU, and a paper is being written with coauthors Jun Sato and Hugh Hudson. Nitta also reviewed the BCS Ca XIX spectra for two-dozen flares in AR 7260, and concluded that there was significant blueshifted emission in most of them and that the loops had significant inclinations. This is in a way consistent with the result from the study of the loop top source. Pevtsov used KPNO and Yohkoh SXT data of three active regions to study if the differential rotation/photospheric shear motions may introduce shear in the coronal loops. In all three cases studied so far, there is no indication that the differential rotation is responsible for the sheared loops. Wuelser presented the paper "EIT and YOHKOH Observations of Solar Flares" with co-authors Metcalf, Lemen, and Moses and the SPD/AGU meeting. In two limb flares, a couple of EIT images of the impulsive phase were obtained in addition to the Yohkoh flare mode data. The main (surprising) finding was bright EIT loop-top sources during the impulsive HXR flare, which didn't have a counterpart in the SXT images. These sources are rather cool (1-2 MK) and therefore not related to the famous superhot loop-top sources. These sources appear to be impulsive, since they do not appear in EIT images during later phases of the flare. They may, however, have some commonality with the recently discovered bright impulsive features in TRACE EUV images at the onset of GOES class-B subflares. Those features are visible only in one image and therefore last less than one minute. Their temperature is also similar to the temperature of the EIT loop-top sources. << 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 Lockheed SXT WWW homepage (http://www.space.lockheed.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 May were 73070 accesses and 3713 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 04-May-98 Pass 4: 980504-1447 recovered in the same pass. SXT Bitmap error 07-May-98 Pass 3: 980507-1238 recovered in the same pass. SXT Bitmap error 20-May-98 Pass 4: 980520-1032 recovered in the same pass. Page 4 << Data Flow >> Month Full Frame Images Observing Region Images Received Lost Received Lost Loss % QT FL Tot Thru Feb-96 357986 154788 1480469 361219 1841688 738908 28.54 Mar-96 6908 2869 25437 1460 26897 12274 31.33 Apr-96 7172 2124 45445 671 46116 18848 29.01 May-96 6925 2426 30272 1089 31361 12367 28.28 Jun-96 7515 2723 31952 1536 33488 14521 30.25 Jul-96 5954 1995 29886 4769 34655 12427 26.39 Aug-96 7214 3010 21187 1607 22794 9887 30.25 Sep-96 6904 2618 29906 303 30209 12663 29.54 Oct-96 7405 2853 16463 1842 18305 8034 30.50 Nov-96 7001 2296 24292 5395 29687 9340 23.93 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 7396 1708 27659 18877 46536 9340 16.72 Jun-98 0 0 0 0 0 0 NaNQ Total 545672 206181 2202663 471601 2674264 989864 27.01 Number of Full Frame Images Received: 545672 Number of Observing Region Images Received: 2674264 Total: 3219936 Approximate Number of Shutter Moves/CCD Readouts: 5597872 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 (%) Mar-96 50.85 762.9 136982 8973 20.3 N/A Apr-96 51.14 773.6 142250 9500 19.9 N/A May-96 51.16 774.4 140697 10018 19.1 N/A Jun-96 51.56 789.2 147705 10634 20.7 N/A Jul-96 57.45 1010.2 146293 12228 19.8 N/A Aug-96 52.58 827.5 165676 12393 19.6 N/A Sep-96 52.47 823.3 162784 12350 20.0 N/A Oct-96 52.21 813.8 157689 12047 22.5 / 2 21.3 N/A Nov-96 52.45 822.9 161683 12534 21.9 N/A 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 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-MAY-98 and 31-MAY-98 HUDSON 10-MAY-98 19-MAY-98 10 31-MAY-98 31-MAY-98 * 1 (total of 11 days) MCKENZIE 1-MAY-98 * 31-MAY-98 * 31 (total of 31 days) SHIRTS 8-MAY-98 15-MAY-98 8 (total of 8 days) SLATER 8-MAY-98 18-MAY-98 11 (total of 11 days) ---------------------------------------------------------------- Grand Total of 61 days for 4 people NOTE: The "*" signifies travel that actually ends after 31-MAY-98 SXT Foreign Travel between 1-JUN-98 and 30-JUN-98 HUDSON 1-JUN-98 * 21-JUN-98 21 26-JUN-98 30-JUN-98 * 5 (total of 26 days) MCKENZIE 1-JUN-98 * 29-JUN-98 29 (total of 29 days) ---------------------------------------------------------------- Grand Total of 55 days for 2 people NOTE: The "*" signifies travel that actually ends after 30-JUN-98 Respectfully submitted, Thomas R. Metcalf Frank Friedlaender Page 7 ================================================================= Montana State Univ Activity Report for April 1998-May 1998 ================================================================= (M. A. Weber) Much of the work of the MSU Solar Group this period has been organized around preparation for the AGU/SPD Spring Meeting (May 26--29). However, progress was also made on the research and outreach fronts, and efforts are proceeding to increase the SXT team at MSU. Overall, this has been a very productive two months. NEW TEAM MEMBERS Acton reports that the appropriate permissions have been gathered to send a formal letter to NASA requesting that Markus Aschwanden, Terry Forbes, and Judith Lean be considered as SXT Co-Investigators. Meanwhile, Canfield has written and submitted an advertisement for a new SXT scientist at the Assistant/Associate Research Professor level. OUTREACH Acton continued to support the future of solar research by working on the current MODA deficit in the NASA appropriations bill for the Solar Maximum Mission during a trip to Washington, D.C. He was there to take part in a review of proposals for the new "Solar Influences on Global Change" program. McKenzie, Larson, and Slater presented the YPOP (Yohkoh Public Outreach Project) site at a meeting of the National Science Teachers Association, where it was very well- received by the attendant educators and curriculum writers. Canfield and Slater are working with Craig Deforrest (SOHO), Sara Gibson (SOHO), and Hudson to set up a Space Science Update on the sigmoid-arcade patterns that are associated with halo coronal mass ejections. The SSU is tentatively scheduled for late June to mid-July, to coincide with the submission of a paper on the quantitative aspects of these recently discovered patterns as a prediction tool. Weber prepared a short presentation of solar research at MSU for some visitors from Central Washington University, although the tour was later canceled. Acton gave a lecture on his career in physics for the MSU Physics-500 class. The purpose of this class is to acquaint first-year physics graduate students with the research opportunities in the department. SERVICE McKenzie traveled to ISAS at the end of April for a two month tour of duty as SXT Chief Observer. This has been a very busy period for SXT operations, as it included supporting observations for SOHO JOPs 82, 59, 80, and 75. In addition, there were observations to hunt for jets and to characterize better the CCD dark current. Canfield was also at ISAS (April 18--30) and lent a hand as a Yohkoh SSOC tohban. He also served as the Yohkoh Duty Scientist for Mees. Davey was still at ISAS at the beginning of April, where he assisted Freeland in accommodating the computer systems to the needs of the Coordinated Data Analysis Workshop. For Davey, a lot of the past two months has been spent on Page 8 upgrading our Sun systems to Solaris 2.6, and on configuring a new SGI machine. He has been amply helped with his system administration tasks by student Aaron Benner. Acton has been involved with the planning and software coding to remake the SXT movie using our best corrective techniques. RESEARCH Acton, Longcope, and Lundberg worked on a program to display x-ray loops of arbitrary geometry, temperature, and emission measure as they might be seen by SXT or Super-X. Undergraduate Sean Sandborgh, working with Canfield and Pevtsov, looked at the chirality of isolated flux systems using SXT images (see PAPERS...). An examination of large and persistent areas indicates that the hemispheric helicity rule is weak. They speculate that these structures are directly related to giant cells in the convective zone, recently discovered by SOHO. Pevtsov continues to use Kitt Peak and SXT data of active regions to study what role photospheric differential rotation may play in shearing coronal loops. No strong causal connection is indicated. McKenzie is finishing up a paper on filament activation, and is contributing to an Astrophysical Letter, with Acton, Harvey, and Hudson, on bright soft x-ray features which seem to lie along the axes of filament channels. The fact that these regions are bright is hard to understand, since they are thought to be magnetically isolated from the superhot (approx. 1 keV) corona. Weber, under Acton's guidance, explored using the extensive SXT database to produce a temperature related characterization of the corona as a function of time and latitude. A preliminary side result considered the extent and typical emission levels of different classes of the SXR corona, and found the intriguing suggestion that "inter-active region loops" may maintain a relatively constant level of emission throughout the decline of the last activity cycle. Finally, Canfield worked with Hudson on sigmoidal structures in the SXT data from 1997. MEETINGS The 1998 AGU/SPD Spring Meeting in Boston was attended by many members of the MSU Solar Group: Canfield, Handy, Kankelborg, Larson, Longcope, Pevtsov, Sandborgh, Weber, and Welsch. Canfield and Pevtsov are also looking forward to the upcoming Chapman Conference on Magnetic Helicity in Laboratory and Space Plasmas, for which they are Scientific Organizers. The meeting is to be held in Boulder in July (see http://www.agu.org/meetings/cc98bcall.html). PAPERS and ABSTRACTS ACCEPTED or PRESENTED "Magnetic Reconnection, Magnetic Helicity, and Solar Coronal Eruptions", R. C. Canfield, A. A. Pevtsov, and K. P. Reardon. Published in Solar Flares and Related Disturbances (ed. E. Sagawa and M. Akioka), Hiraiso Solar Terrestrial Research Center, Communications Research Laboratory, Japan, p. 15. "Physical Structure of a Coronal Streamer in the Closed Field Region Observed from UVCS/SOHO and SXT/Yohkoh", J. Li, J. C. Raymond, L. W. Acton, J. L. Kohl, M. Romoli, G. Noci, and G. Naletto. Accepted by The Page 9 Astrophysical Journal. "Chirality of Large-Scale Flux Systems in the Solar Corona", Sean C. Sandborgh, Richard C. Canfield, and Alexei A. Pevtsov. Presented at the Second Undergraduate Research Poster Session on Capitol Hill, Council on Undergraduate Research, April 21, 1998. Also presented at the 1998 AGU/SPD Spring Meeting in Boston, MA, May 26--29, 1998. Abstract published in EOS, Transactions, American Geophysical Union, 1998 Spring Meeting, Vol. 79, No. 17, April 28, 1998 supplement, p. S285. "The Eruptive Flare of 15 November 1991: Preflare Phenomena", Richard C. Canfield and Kevin P. Reardon. Accepted by Solar Physics, May 18, 1998. "On the Origin of Helicity in Active Region Magnetic Fields", A. A. Pevtsov and R. C. Canfield. Abstract published in Observational Plasma Astrophysics: Five Years of Yohkoh and Beyond (ed. T. Watanabe, T. Kosugi, A. Sterling), Kluwer Academic Publishers, Dordrecht, p. 85. "Do Photospheric Motions Cause Sheared Loops?", A. A. Pevtsov, R. C. Canfield. Presented at the 1998 AGU/SPD Spring Meeting in Boston, MA, May 26--29, 1998. Abstract published in EOS, Transactions, American Geophysical Union, 1998 SpringMeeting, Vol. 79, No. 17, April 28, 1998 supplement, p. S273. "Emission Levels of the Diffuse and Inter-Active Region Corona in Soft X-Rays", M. A. Weber and L. W. Acton. Presented at the 1998 AGU/SPD Spring Meeting in Boston, MA, May 26--29, 1998. Abstract published in EOS, Transactions, American Geophysical Union, 1998 SpringMeeting, Vol. 79, No. 17, April 28, 1998 supplement, p. S293. "Bringing Solar Science to the Public: The Yohkoh Public Outreach Project", T. Slater, M. B. Larson, D. McKenzie, L. W. Acton, D. Alexander, S. Freeland, J. R. Lemen, and T. R. Metcalf. Presented at the 1998 AGU/SPDSpring Meeting in Boston, MA, May 26--29, 1998. Abstract published in EOS, Transactions, American Geophysical Union, 1998 SpringMeeting, Vol. 79, No. 17, April 28, 1998 supplement, p. S251. "Data Analysis with the SolarSoft System", S. L. Freeland and B. N. Handy. Accepted by Solar Physics, 1998. ============================================================= Univ of Hawaii Activity Report for April 1998-May 1998 ============================================================= (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 Page 10 Manoa. Our colleagues Mickey at Manoa, Canfield at Montana State University, Wuelser and Metcalf at Lockheed Martin, and Hudson at Solar Physics Research Corporation aided in advice and oversight of Mees operations. Weather during this interval has been good. All instruments are working well. During this interval we conducted cross-training of the Mees Observatory technical staff to enable them to conduct observations when the regular observer G. Nitta is on leave. This has already helped to provide coordinated observations with the joint TRACE-SOHO-YOHKOH observing campaign at the end of May. Graduate student L. Jiao successfully defended his PhD thesis in May. The thesis, entitled "Reconstruction of the Three-Dimensional Solar Coronal Magnetic Field", compared YOHKOH SXT images of coronal structure with computed models of the coronal magnetic field. The models used Mees Solar Observatory vector magnetograms as a boundary condition and modeled the coronal fields with the evolutionary, nonlinear, non-constant alpha force-free approximation. Jiao made nearly two dozen extrapolations for six active regions and activity complexes with a range of magnetic complexity and flare productivity. Among the results that Jiao found are: the computed magnetic free energy scales with the flare productivity; there is substantial coronal structure at low altitudes and small scales that contribute to the structures seen by SXT and is at or below the resolution limit of the field extrapolations even in the "simplest" bipolar regions; separatrix locations determined from the field extrapolations show small, isolated features that sometimes match with the locations of flare kernels or unusually bright SXT loops; many general features of the coronal field can be matched with incomplete vector field data, which covers only one polarity of an active region, if a longitudinal field map exists for the whole region. LaBonte participated in the joint SOHO-YOHKOH Coordinated Data Analysis Workshop at ISAS in April, leading working group 1. The group was able to identify and confirm a uniquely well observed polar crown filament that is seen to include a dense coronal core inside a low density cavity. Tomography of this structure is possible from the SXT data, and work on it is continuing. LaBonte and Mickey presented papers at the Joint AGU-SPD meeting in May based on Mees data taken in coordination with YOHKOH. PAPERS PRESENTED: Probing the Subsurface Structure of Active Regions with Acoustic Imaging. B. J. LaBonte (U. Hawaii), H.-R. Chen, D.-Y. Chou, H.-K. Chang (Tsing Hua U.), M.-T. Sun( Chang-Gung U.), S.-J. Yeh (Tsing Hua U.), and the TON Team Joint AGU-SPD. A Search for Flare-Related Changes in Photospheric Magnetic Fields. K. D. Leka (Colorado Res. Assoc.), P. L. Bornmann (SEC/NOAA), D. L. Mickey, B. J. LaBonte (U. Hawaii), Joint AGU-SPD Page 11 A Quantitative Performance Characterization of the Imaging Vector Magnetograph at Mees Solar Observatory. D. L. Mickey (U. Hawaii), K. D. Leka (Colorado Res. Assoc.), B. J. LaBonte (U. Hawaii), Joint AGU-SPD OTHER PAPERS USING MEES COORDINATED OBSERVATIONS: OVRO and NRO Observations of a Solar Flare. J. Lee (U. Maryland), D. E. Gary (NJIT), Joint AGU-SPD ============================================================ Stanford Univ Activity Report for April 1998-May 1998 ============================================================ (P. Sturrock) We report with regret that Mike Wheatland has left Stanford University to take up a Fellowship at Sydney University. This is an honor and a step forward for Mike, but a real loss to the Stanford Program. However, Mike plans to continue some of his Yohkoh research in his new home. We are fortunate that Colin Roald, now at Rochester University where he has been studying with Jack Thomas, will be joining us in July. Colin has made an extensive study of the solar dynamo, and wrote a dissertation on Nonlinear Solar Dynamo Models with Magnetic Back-Reactions. Peter Sturrock still has real concerns about the validity of mean-field electrodynamics, that is the basis of most dynamo models, so Colin and Peter should be able to pursue an interesting debate on this topic. Peter is developing his work on coronal heating into an article. The basic concept is that reconnection between two contiguous flux tubes is most likely to occur at or near the temperature-minimum region. As a consequence, reconnection will lead to the sudden eruption of newly formed flux tubes that carry chromospheric gas into the corona. Vibration of the flux tubes generates sound waves that heat the surrounding coronal gas. An interesting property of this model is that the reconnection is likely to form quite thin strands of magnetic flux (a few km in diameter). We find that fractionation is likely to occur when cool gas is carried along in a rapidly accelerating flux tube of this size: ionized particles are swept along, but neutral particles tend to be left behind. Hence this model seems to offer an explanation of the FIP (first ionization potential) effect. We plan to examine this mechanism in more detail. This model leads us to expect a scaling relationship between the coronal X-ray flux and the photospheric magnetic field strength. One simple version of the model leads to a a linear relationship, and another simple model leads to a quadratic relationship. The data-set analyzed by Loren in his presentation to the Cool Stars conference in Florence yields a quadratic relationship. We plan to carry out some computer simulations of a wider range of models. As a way of pursuing this topic, Mike and Peter have completed part of a Page 12 collaborative investigation involving Sasha Kosovichev and Rick Bogart 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. Soft-ray data (from SXT images) and magnetic flux measurements (from MDI full-disk magnetograms) will be compared, for a small region around disk center (0.2 by 0.2 solar radii), for a period of two months. As a first step, a week's worth of Yohkoh data has been extracted, and luminosity estimates have been made for that data. Next, comparison will be made with the MDI data for the same region, and in particular the histograms of magnetic flux values will be examined, to determine if a detailed relationship between magnetic flux and soft X-ray flux exists. Mike Wheatland continues to work on methods of reconstructing the magnetic field in the solar corona from the observed boundary values (inferred from polarization measurements in the low atmosphere). He is developing a non-linear method (based on an optimization approach) as well as investigating a means of using the non-uniqueness of the linear problem to obtain a "best" linear force-free field. Sang-Hyun Kim is finishing up his analysis of loop-like structures in one of the diffuse coronal regions previously analyzed by Mike and Peter in their collaboration with Loren Acton. Sang-Hyun is considering a range of possible geometries, and different hypotheses concerning the heating function, and comparing the expected flux from these models with SXT data, with a view to determining whether the heat input was distributed or localized. Peter also retains an interest in the apparent rotational and latitudinal modulation of the solar neutrino flux. If real, this probably points to a latitudinal and longitudinal structure of the deep solar magnetic field, possibly in the radiative zone. This raises the question of whether that field also influences activity at the surface of the Sun. Peter is looking for a way to examine this possibility. It also appears that the Rieger periodicity (155 days) shows up in the neutrino flux (as well as in all kinds of activity data, including soft and hard X-rays). Peter is collaborating with Taeil Bai of the MDI team on this matter, and they are looking into the possibility that the Rieger periodicity may be caused by a Rossby-wave-type disturbance, and into the possibility that such a wave might be detectable in SXT-type data. Papers accepted for publication Apparent Latitudinal Modulation of the Solar Neutrino Flux by P. Sturrock, G. Walther & M. Wheatland. (Ap. J.) Papers submitted for publication The Waiting-time Distribution of Solar Flare Hard X-ray Bursts, by M. Wheatland, P. Sturrock & J. McTiernan (Ap. J.) Page 13 =========================================================================== Solar Physics Research Corp. Activity Report for April 1998-May 1998 =========================================================================== (Karen L. Harvey and Hugh S. Hudson) KAREN L. HARVEY: Activities for April and May: (1) Continued study of the magnetic field and coronal hole evolution of the active region complex that occurred during several rotations in the summer 1996 and preparation for a paper presented at the May SPD/AGU meeting in Boston. The analysis focused on trying to understand the formation of several coronal holes in relation to the emergence and dispersal of magnetic flux in the activity complex located around S10 and in two new cycle regions at latitudes >N25. The large coronal hole that extended from the north polar hole to the activity complex resulted from a sequence of occurrences: the eastward shift of the emergence of four of the five regions (mid June to late July) in the complex to the follower fields of the original region (which emerged April 20), the emergence of a moderately large new cycle region (mid June) at N25, the reconnection of its follower negative polarity fields to the opposite polarity polar fields, the eastward shift of this new cycle region in longitude due to differential rotation, and the eventual alignment of the leader positive fields of this new cycle region and the leader positive fields of the original old cycle region in the complex (mid August). (2) Collaboration between NSO/KP, Yohkoh/SXT, SOHO, TRACE, BBSO during an observing program 4-6 May 1998 to study whether magnetic flux in quiet sun canceling bipoles is submerging below the photosphere or continuing to rise through the photosphere. The magnetic field observations at NSO/KP were made simultaneously in two lines: the CaII 8542 chromospheric line and the FeI 8538 photospheric line. The separation in height between the two lines, about 2000 km, should be sufficient to determine flux differences at these two levels of the atmosphere as a function of time. The intensity and velocity data obtained in other lines and spectral regions provides the needed input on the response of the chromosphere and corona to the cancellation of magnetic flux. (3) Worked with Hugh Hudson, Loren Acton, and David McKenzie on the analysis of and a paper reporting on the coronal cavity observed by the SXT during June to August 1997. This paper was just submitted to ApJ. (4) 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. (5) Updating the Yohkoh bibliography. Planned Activities for June and July: The analysis of the magnetic fields and coronal holes related to the 1996 activity complex and the large scale field patterns will continue and will be Page 14 written up for publication. This includes determining the how the coronal connections, based on the SXT data, to the photospheric magnetic field developed over several months as this complex and the new cycle regions evolved. An investigation of the magnetic field evolution around the filament channel observed as a coronal cavity in 1997 will continue. The analysis of the XBP data collected during several observing campaigns, particularly the more recent ones, will continue. One additional joint observing campaign for the study of canceling bipoles will occur 14-17 June. Papers Submitted Hudson, H. S., Acton, L. W., Harvey, K. L., and McKenzie, D. E.: "A Stable Filament Cavity with a Hot Core", ApJ, June 1998. HUGH S. HUDSON Activities in April and May Hudson's research effort mainly focused on the sigmoid signature of CMEs and the (perhaps not unrelated!) hot cores in filament channels. The latter subject was presented at the SPD meeting in May, and the initial paper describing the SXT observations has been submitted to ApJ Letters. The initial indication is that the core is hot, even though quiescent, and this (among other things) favors the idea that the X-ray emission is related to the dynamics of filament maintenance. Hudson also spent one week at GSFC observing the TRACE/SOHO operations, and took the opportunity to work on Dick Canfield's idea of an SSU (Space Science Update) that would feature the SXT sigmoids and the Gibson-Low model that can represent them - the key being that this signature has given us a leg up on CME prediction. Plans for June and July Helping Canfield with a sigmoid AR morphology paper has the highest priority, since this is related to our understanding of the scientific content of the SSU. After this in priority - preparations for COSPAR, where Hudson foolishly had submitted five abstracts. Many visitors will be around ISAS near the time of the meeting, so most of the preparation for the presentations will have to be done by early July. There are many important further steps needed to develop our analysis of the "chewy nougat" (cavity hot core) phenomenon. A second SXT paper (effort led by McKenzie) should sharpen our knowledge of the physical conditions in the cavity. The preliminary work suggests that there's a higher vacuum in such a region than in the solar wind at the corresponding altitude. How can this be, when the solar-wind corona is vented to free space? Probably the answer lies less in the quality of the vacuum pump, than in the extent of the leaks in the system! Papers published Page 15 Galvin, A. B., and Hudson, H. S.: "An Overview of IACG Campaign 4: Solar Sources of Heliospheric Structure Observed out of the Ecliptic", ESLAB-97 (1998), 38-46 Hudson, H. S., and Galvin, A. B.: "Correlated Studies at Activity Maximum: The Sun and the Solar Wind", ESLAB-97 (1998), 275-282 Bothmer, V., Posner, A., Kunow, H., M\"uller-Mellin, R., Delaboudiniere, J.-P., Thompson, B., Brueckner, G. E., Howard, R. A., Michels, D. J., Mann, G., Classen, H.-T., and Hudson, H. S.: "Solar Energetic Particle Events and Coronal Mass Ejections: New Insights from SOHO", ESLAB-97 (1998), 207-216 Svestka, Z., Farnik, F., Hudson, H. S., and P. Hick: "Post-Flare Loops Embedded in a Hot Coronal Fan-Like Structure", ESLAB-97 (1998), 139-144 Simnett, G. M., and Hudson, H. S.: "The Evolution of the Coronal Mass Ejection on February 23, 1997", ESLAB-97 (1998), 437-442 Papers Submitted Hudson, H. S., Acton, L. W., Harvey, K. L., and McKenzie, D. E.: "A Stable Filament Cavity with a Hot Core", ApJ, June 1998. 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 June 1998 May 1998 |------------------------------- | 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: John Owens | of May 1998 |------------------------------- |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