Page 1 PROGRESS REPORT THE SOLAR-A SOFT X-RAY TELESCOPE (SXT) PROGRAM (CONTRACT NAS8-40801) (for March 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 Programmatic issues were nominal this month. The program is currently adequately funded to provide both operations and data analysis support for 1999. A visit to MSFC is planned to discuss continued support through solar max. << Solar Activity >> In early March, there were twenty or more C-class events, but only one M-class event. The North-South interconnecting loops that had been so remarkable in the previous two weeks were behind the limb, and did not reappear. It may be that the trans-equatorial loop visibility comes and goes with the active regions, in spite of the strong tendency for these structures not to link the core fields of these regions. In mid-March, there were eleven M-class events, dominated by AR8485 and 8487. The AR8485 spot group reached 610 millionths in area on the 17th. The disappearance of these regions caused a precipitous drop in the GOES flux level on the 19th. Choosing between the two competing regions was the tricky part of the coordinated observations during the period! At the end of March, the low level of solar activity was unprecedented in the current cycle. There were three M-class events at the end, but in the meanwhile, for a period of ten days, only one C-class flare occurred! Of course this is good news, as it means a bit of a postponement of Yohkoh's final re-entry, and more of an overlap with HESSI (to be launched July 4, 2000). << Campaigns >> In early March, there were no formal coordinated observations. SXT Page 2 co-observed with TRACE and SOHO in an attempt to find clean loops, not confused with foreground/background features, for modeling by Jim Klimchuk. We also tried to follow VLA targets, but were hampered by poor communication. In mid-March, SXT co-observed with TRACE and SOHO (CDS) in an attempt to observe preflare signatures (N. Ranns, MSSL). Between AR8485 and 8487 there was plenty of activity, but as is well-known, preflare signatures have been shown by earlier Yohkoh studies to be perplexing in their capriciousness and possible irrelevance. But theoretically, this should not be the case. Perhaps the sigmoids are telling us something different about preflare arrangements for flares. << Science >> Acton, Metcalf, Freeland and Lemen worked on final preparations for the new SXT science composite movie. This movie will have no compression and improved corrections. Alexander and Fletcher participated in the PBS 'Live from the Sun' online discussion. Live from the Sun is an interactive learning adventure from the award-winning Passport to Knowledge (PTK) series. Live from the Sun features the most recent discoveries about the Sun, and will continue with updated Web and video materials through Solar Maximum. During the live program students have the opportunity to submit questions in real time to NASA researchers, National Solar Observatory astronomers at Kitt Peak and other experts. Canfield participated in the "S Marks the Spot" NASA Space Science Update, which got extensive national network (CNN, CBS), local TV (approximately 60 local stations), and worldwide press coverage. The best web and print articles were from Scientific American and the Washington Post (see http://solar.physics.montana.edu). On March 18, 1999, SXT observed a beautiful cusp structure on the NE limb of the Sun. We've seen many cusps before, and there is abundant literature describing this pattern as observed by Yohkoh SXT. In particular people remark that the cusp configuration implies an open field configuration above the bright loops. In this manner oppositely-directed fields would be juxtaposed and magnetic reconnection could occur. Or if not "open" field lines, which makes a statement about solar-wind flow, the geometry would have a great elongation so that a current sheet could form. The reconnection thus expected could in principle feed energy into flare loops following the ejection of a plasmoid - the standard model of eruptive flare development. This March 18 cusp illustrates a couple of points that are troubling pointing out. Indeed, these conflict somewhat with what common sense would tell us about the standard picture. First, there is a structure beneath the cusp and second the cusped structure is not an arcade, but a single loop. Both of these characteristics have been noted before - in the celebrated "candle flame" flare of Feb. 21, 1992, the interior structure appeared to have a cusp shape of its own. The standard model does not include such a structure. As for the planarity of the large-scale cusp: this sounds quite odd Page 3 from the MHD point of view. This cusp followed a CME, as reported by LASCO. The Yohkoh data cover the launch of the CME and extend for several days. One can see the pre-event corona, followed by dimming and the formation of a tall feature with a frayed top, followed then by the better-organized cusp. As invariably happens, the cusped feature appears late in the event, grows larger and dimmer, and eventually disappears into the background coronal brightness. These features are all appropriate to the large-scale reconnection picture of the eruptive flare/CME phenomenon. However, solar rotation gives us different perspectives during the three-day sequence, and from this it's clear enough that the cusp feature is not an arcade, but a single loop surmounted by a helmet spike. In fact, several questions arise: Question #1: If the cusp geometry implies reconnection, why did it develop long after the major energy release (the CME)? Question #2: What can we make of the structure beneath the cusp - is it evidence for some sort of "tether cutting", in which case should we identify the loops themselves with the plasmoid of the standard model? Question #3: If the basically 2-dimensional model of inflow into a Petschek-type reconnection is to explain this observation, why is the inflow restricted to such a short arcade (apparently only a single loop structure)? << 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 March were 96006 accesses and 5568 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 20-March-99 Pass 2: 990320-0620 recovered in same pass. Page 4 << Data Flow >> Month Full Frame Images Observing Region Images Received Lost Received Lost Loss % QT FL Tot Thru Jan-97 435314 183092 1781766 383235 2165001 869596 28.60 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 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 1373 203 4925 2937 7862 1215 13.39 Apr-99 0 0 0 0 0 0 -NaN May-99 0 0 0 0 0 0 -NaN Total 603290 222387 2426072 588740 3014812 1079501 26.37 Number of Full Frame Images Received: 603290 Number of Observing Region Images Received: 3014812 Total: 3618102 Approximate Number of Shutter Moves/CCD Readouts: 6230985 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 (%) 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 57.01 993.7 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 58.56 1051.7 224462 36931 21.4 N/A Apr-99 N/A N/A N/A N/A 0.0 N/A May-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-MAR-99 and 31-MAR-99 ACTON 1-MAR-99 * 2-MAR-99 2 (total of 2 days) DAVEY 17-MAR-99 28-MAR-99 12 (total of 12 days) HUDSON 1-MAR-99 * 6-MAR-99 6 11-MAR-99 31-MAR-99 * 21 (total of 27 days) NITTA 21-MAR-99 31-MAR-99 * 11 (total of 11 days) SHIRTS 15-MAR-99 31-MAR-99 * 17 (total of 17 days) ---------------------------------------------------------------- Grand Total of 69 days for 5 people NOTE: The "*" signifies travel that actually ends after 31-MAR-99 SXT Foreign Travel between 1-APR-99 and 30-APR-99 CANFIELD 24-APR-99 30-APR-99 * 7 (total of 7 days) HUDSON 1-APR-99 * 24-APR-99 24 (total of 24 days) MCKENZIE 21-APR-99 30-APR-99 * 10 (total of 10 days) NITTA 1-APR-99 * 16-APR-99 16 (total of 16 days) SHIRTS 1-APR-99 * 10-APR-99 10 (total of 10 days) LABONTE 6-APR-99 22-APR-99 17 (total of 17 days) ---------------------------------------------------------------- Grand Total of 84 days for 6 people NOTE: The "*" signifies travel that actually ends after 30-APR-99 Respectfully submitted, Thomas R. Metcalf Frank M. Friedlaender Page 7 7 ======================================================================= Montana State University Activity Report for February 1999-March 1999 ======================================================================= (M. Weber) INTRODUCTION The MSU group carried out SXT operations, data analysis, graduate and undergraduate research, and meeting organization. Two noteworthy items of this reporting period are the participation of Richard Canfield in a NASA Space Science Update regarding the prediction of solar eruptions from sigmoidal structures on the Sun, and Rebecca McMullen has accepted an offer to begin graduate studies at MSU in the fall. McMullen has done promising undergraduate work with TRACE data and our Solar Group is looking forward to working with her. We also wish Loren well on the occasion of his retirement from his full-time Research Professor position at MSU, effective April 1, 1999. YOHKOH AND SXT OPERATIONS McKenzie's term as SXT Chief Observer finished in mid-February. Acton spent the month of February in Japan working on SXT calibration issues, mostly on the ramifications of the SXT entrance filter failures on the data. In the process he uncovered some errors pertinent to the planned regeneration of the SDC and SFC databases. Acton also supported McKenzie in an investigation of practical limitations on SXT vignette corrections. Davey traveled to ISAS to assist with the complicated convergence of user accounts on the ISASS# machines. Canfield served as Mees Yohkoh Duty Scientist during the second and fourth weeks of February. RESEARCH Acton has spent much effort on trying to improve calibration of the effect of SXT entrance filter failures as they affect derivation of, e.g., temperature and spectral irradiance. In the process, he has realized that, rather than matching filter-ratio temperatures one has to match model-derived DEM-averaged temperatures. Furthermore, his investigation of the "zeroth" entrance filter failure on 27-Oct-92 shows that the thin filter signals increased by 29% (!) at the poles at the time of this event while the AlMg/Al.1 ratio temperature dropped from 2.14 to 1.87 MK. He concludes that this is a priority calibration problem. Since returning from Japan, he has reviewed galley proofs for a paper on deriving solar X-ray irradiances, investigated utility of SXT offpoints for future UVCS/SXT campaigns, and contributed to the final preparations of the new and improved SXT science composite movie. Canfield worked with Angela Colman to adapt Kevin Reardon's software for velocity measurements prior to eruptive flares to the MSU computer system and the current version of IDL. Piet Martens and Charles Kankelborg have been developing analytical models for the "moss" that has been observed by TRACE in the 171 A line at about 1 MK, Page 8 almost uniquely at the footpoints of much hotter (3-5 MK) and larger loops observed by SXT. Their comparison of two analytical models with emission measures observed by TRACE and SXT favor the interpretation of "moss" as being legs of larger loops (observed by SXT) rather than being very small loops below TRACE's resolution. They plan to publish their results in a Letter to Solar Physics. McKenzie spent a lot of time with Hugh Hudson studying motions and structures in the 20-Jan-99 arcade. They've seen coronal dimming, loop shrinkage, a fan of rays above the arcade, and infall of dark blobs; the manuscript is almost ready for submission. The scattered light corrections were found to be problematic in making accurate temperature maps with filter ratios, but he was able to manage a point-spread function compensation. Weber finished a draft of a paper on measuring the differential profile of the corona's rotation rate, and has sent it out to the co-authors. The results for the rotation rates are as expected, but there is an additional result that the tracer features move at varying rates, even within the same latitude and time bin, and this places a bound on the precision with which a single rotation rate can be determined. He is also studying the effects of flux emergence on the boundaries and rotation rates of coronal holes. SERVICE AND OUTREACH Acton made two school appearances, one at Skyview High School in Billings, and one at Headwaters Academy in Bozeman. He also participated in some telephone interviews in connection with public response to the NASA Space Science Update on Sigmoids. Canfield spent time on an overview article on active regions for the McMillan/Institute of Physics encyclopedia and hosted the visit of a potential graduate student. His largest project (during this period) was his involvement in the ``S Marks the Spot'' NASA Space Science Update on sigmoids on March 9, 1999, which got extensive national network (CNN, CBS), local TV (approximately 60 local stations), and worldwide press coverage. He worked with Phil Shirts on videos, worked with Dave McKenzie to update the web page (http://solar.physics.montana.edu/press), and worked with Annette Trinity-Stevens on the press release. Other notes of service include: meeting with the physics long-range planning committee and several college of engineering department heads on the Space Science and Engineering Laboratory initiative, preparing a budget for Phase II of YPOP at MSU, and refereeing papers for ApJ Letters and NSF. Davey has supported the SXT computing environment at MSU by furthering the extent of the security measures, apparently necessary since he has documented frequent break-in attempts to MSU machines. There have been problems with some of the data storage devices, but these have been addressed. McKenzie contributed effort towards the Space Science Update regarding sigmoid morphology and solar eruptions. He gave voice and face to the MSU TV crew, plus a telephone interview with the MSU press liason, Annette Trinity-Stevens. He was also responsible for creating and maintaining webpages Page 9 at MSU to support the SSU. On a related note, Samantha Allen took First Place in the Harlem High School science fair, at which she presented her work on sigmoids which was done here at MSU as a summer project. Papers Published: Canfield, R. C., Hudson, H. S., and McKenzie, D. E., ``Sigmoidal Morphology and Eruptive Solar Activity'', Geophysics Research Letters, Vol. 26 , No. 6 , p. 627, 1999. Papers Submitted: Canfield, R. C. ``Solar Active Regions'', in ``Encyclopedia of Astronomy and Astrophysics'', Institute of Physics, submitted, 1999. Talks/Posters Given: ``Conversion of SXT Fluxes to Irradiances'', Loren W. Acton, Yohkoh Seminar, Institute of Space and Astronautical Science, Japan, February 25, 1999. ``Analysis of SXT Entrance Filter Failures'', Loren W. Acton, Yohkoh Seminar, Institute of Space and Astronautical Science, Japan, February 25, 1999. ``Impromptu Talk on Reconnection Topology'', Loren W. Acton, Sturrock 75th Birthday Symposium, Stanford, March 20, 1999. ``The 20-Jan-99 Arcade Flare'', David E. McKenzie, MSU Solar Journal Club, Bozeman, March 10, 1999. ``The Yohkoh Public Outreach Project: Studying the Sun Using the Internet'', Tim Slater, Michelle Larson, and David McKenzie, Northwest Council for Computers in Education Conference, Seattle, March 19, 1999. ============================================================= Univ of Hawaii Activity Report for February 1999-March 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 Page 10 Research Corporation aided in advice and oversight of Mees operations. Weather at Mees improved greatly in March with prospects for a decent spring and summer. Changes in the Mees instrument status during this interval include: Imaging Vector Magnetograph down for the upgrade of the CCD cameras, reassembled and test observations in progress. The Hawaii workstation at ISAS, kopiko (isass6) failed and a replacement has been shipped to ISAS. Jing Li has continued her work on the comparison of SOHO/UVCS and Yohkoh/SXT temperature diagnostics as a function of height. She has found different behavior between streamer and non-streamer regions. She has been analyzing data from 1996, when the low level of solar activity made the comparison difficult; the altitude at which the two instruments' field-of-views overlap is several tenths of a solar radius above the limb and the SXT flux was low. With the increase in activity and the recovery of SOHO, the opportunity for new observations has occurred. Li and LaBonte are now planning a joint observation between SXT and UVCS. Analysis of the SXT leak images and the options for an offpoint are currently in progress with the help of Acton and Hudson. LaBonte, Mickey, and Leka (Colorado Research) submitted, finally, a paper describing the performance of the Mees Imaging Vector Magnetograph and the correction of its data for instrumental and atmospheric effects. The IVM was found to compare favorably with the Advanced Stokes Polarimeter in the ability to measure Stokes spectra, given the spectral and spatial resolutions, once the data are fully corrected. LaBonte is continuing work on the analysis of AR8210 in April-May 1998. The magnetic character of the region and the nature of the flare activity abruptly changed during the disk passage. The early days showed large-scale shear, and produced a few, X-class flares that completely cleared the magnetic flux system. The post-flare X-ray flux dropped below the preflare, and no small flares were produced for roughly 24 hours. This behavior is like a relaxation oscillator. On 29 April, flux emergence began in the region, producing magnetic complexity and a large number of small flares. Detailed comparison of the flux emergence, magnetic restructuring, and flare generation is in progress. PAPERS SUBMITTED: LaBonte, Mickey, and Leka. The Imaging Vector Magnetograph at Haleakala. II. Reconstruction of Stokes spectra, Solar Physics. LaBonte. Sky Brightness Measurements at Haleakala, 1955-1998, Geophysical Research Letters. Page 11 ============================================================ Stanford Univ Activity Report for February 1999-March 1999 ============================================================ (P. Sturrock, C. Roald, and R. Wolfson) 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. Roald has developed a numerical model of this process, and computed power-law dependences of the heating flux on the mean magnetic field over a wide range of values of the principal problem parameters. Results for the power-law index typically are surprisingly high, around 1.95 (where analytic considerations lead us to expect it to fall somewhere in the range between 1 and 2). The parameter that appears to have the most influence on the index is the effective diffusivity of the elements over the surface of the supergranule, assumed to result from buffeting by random granular flows. Sturrock has carried out a spectrum analysis of an SXT data set kindly provided by Mark Weber of Montana State University. This set gives daily average values of the SXT flux, as measured by the Al and Dg filters, in nine small regions located at latitudes -60S, -45S ... 45N, 60N. Our simple picture of differential rotation leads us to expect that there will be a single peak, and that the frequency of that peak will drift to lower frequencies as the latitude increases. This is not what we find from the data analysis. Each spectrum shows several peaks. At the equator, the dominant peak is at 13.5 cycles per year, corresponding to a synodic period of about 27.1 days. This is somewhat slower than the surface rotation rate at the equator, 13.51 y^-1, corresponding to a synodic period of 26.76 days. A rotation frequency of 13.5 y^-1 corresponds to the surface rotation rate at a latitude of about 13 degrees. As the latitude increases, we continue to find a peak at about 13.5 y-1, but the strength of the peak decreases. On the other hand, peaks at lower frequencies become stronger. At high latitudes, the dominant peak is at 12.9 y^-1, corresponding to a synodic rotation period of 28.3 days. This is the surface rotation rate at about 30 degrees latitude. This peak is clearly present (at the same frequency) at latitudes 45 degrees and 60 degrees. When we spectrum analyze the total SXT flux, we find that there is a quite sharp peak at the Carrington frequency (13.39 y^-1, synodic), and twice this frequency. The peak is more pronounced for the Dg filter than for the Al filter. These results are quite puzzling. The coronal structure is determined by the surface magnetic field, and surface magnetic features such as sunspots are known to exhibit differential rotation. Yet the SXT measures of coronal Page 12 emission do not exhibit the same behavior. We will be seeking interpretations of these results, and looking for ways to check these interpretations. In pursuit of these questions, and also in support of the coronal heating model mentioned above, Wolfson and Roald has been analyzing correlations between this SXT data set and SOHO/MDI magnetograms from the same 521-day period. Wolfson has binned the MDI data into nine latitude ranges to match the SXT data set, and finds that strong correlations occur at all but the extreme latitudes. The relation between log(x-ray flux) and log(|B|) is a power law with index in the range 1.6 to 1.8 -- somewhat lower than that predicted by the simple model described above. The correlation is due primarily to the relatively few times when the photospheric field and x-ray emission are both strong. Correlations peak when the two time series are correlated with no phase lag, and drop off rapidly for lags of more than a few days. However, strong correlations recur when the data sets are out of phase by multiples of the solar rotation period, indicating the presence of persistent structures in the photosphere and/or corona. A cross-latitude analysis indicates that the high-latitude coronal emission is more closely correlated with the photospheric magnetic field at lower latitudes than with the underlying photosphere--suggesting that the solar magnetic field spreads from lower latitudes at the photosphere to higher latitudes in the corona. Significant correlations between SXT and MDI data in opposite hemispheres also occur, but these disappear when the long term trend in the data--presumably due to the solar cycle--is removed. Roald has frequency-analyzed the MDI data to compare with the SXT frequency spectrum, and finds harmonics of the 13.5 yr^-1 Carrington frequency clearly visible to the tenth order and beyond, and as in the SXT data, that these high harmonics show much less differential rotation than naively expected. With Sturrock, he will pursue a comparative analysis of this photospheric rotation spectrum with the SXT coronal spectrum. =========================================================================== Solar Physics Research Corp. Activity Report for February 1999-March 1999 =========================================================================== (Karen L. Harvey and Hugh S. Hudson) KAREN L. HARVEY: Activities for February and March: (1) Continuing 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. We have been successful in reducing the simultaneous measurements of the magnetic and velocity fields, line depth and equivalent width at two levels of the solar atmosphere: in the chromosphere and photosphere. The lines used are the Ca II 8542 and Fe 8538 lines. The Page 13 data will be analyzed to determine if magnetic flux in canceling bipoles in the quiet sun is submerging below the photosphere or emerging into the solar atmosphere. A detailed comparison will be with intensity images from the SXT, TRACE and SOHO in the X-ray and EUV lines to deduce the height structure of the associated coronal bright points. A talk on the subject is planned for the August TRACE meeting. (2) Prepared an article for an encyclopedia on coronal cavities, making use to the observations of the long-lived cavity seen in SXT images on eight successful limb pages starting on 3 June 1996 to 16 September 1997. Several results from the Hudson et al. paper (ApJ, 515, 83L) on the subject were included. This work along with the results from an analysis of coronal cavity disk counterpart, i.e. filament channels, will also be reviewed at a PROM workshop to be held in Tucson, April 8-10, 1999. (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 April and May: Continued analysis of (1) 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; (2) 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; (3) of filament channels related to coronal cavities, focusing on the 1997 June-September observations and in 1993 February. PUBLICATIONS: Papers Accepted: Harvey, K. L.: 1999, "Coronal Cavities", to be published in an Encyclopedia of Astronomy, Institute of Physics and Macmillan Publishing, United Kingdom. HUGH S. HUDSON Activities for February and March: Hudson's major science activities had to do with "S marks the spot" - the sigmoid => eruption pattern, which under Dick Canfield's guidance became a NASA Space Science Update which is still resulting in communications. The CME-related sigmoid evolution is the subject of another paper being prepared by Alphonse Sterling, with Hudson's help. Page 14 Hudson also has been helping David McKenzie with the interpretation of the 20 January 20 1999 limb arcade event, which resembles the 28 August 1992 event - a spiky fan appears above the arcade loops. The new wrinkle is that we now see abundant mass motions in the fan region itself. This is a most exciting development, because the nature of the flows in this region are crucial to an understanding of the role of reconnection (the "cusp"). The results are surprising, please stay tuned for the initial paper on this subject. Planned activities for April and May: The paper on the May 6, 1998 global flare wave did not quite make it out the door! This is still Hudson's top priority. An abstract on this subject has also been submitted to the AAS/SPD meeting in Chicago. Otherwise, as opinioned in the report two months ago, it would be nice to work on quiet-Sun things (such as interconnecting loops) again. The trouble is that the Sun is just too darn active right now! So there will no doubt be continued interest in ejective flares, CMEs, sigmoids, and (we hope) more of the global flare waves. PUBLICATIONS: Papers Published Lin, R. P., and 40 co-authors (including H. Hudson), "High-Energy Solar Spectroscopic Imager (HESSI) Small Explorer Mission for the Next (2000) Solar Maximum", SPIE 3442, 2, 1998. Hudson, H. S., Acton, L. W., Harvey, K. L., and McKenzie, D. E., "A Stable Filament Cavity with a Hot Core", ApJ 513, 83L, 1999. =========================================================================== Naval Research Laboratory Activity Report for February 1999-March 1999 =========================================================================== (J. Lean) Magnetic Modulation of the Global Solar X Ray Corona We have made further simulations of solar cycle variations of the SXT images and global fluxes utilizing the potential field source surface (PFSS) model with additional parameterizations of heating in terms of magnetic field strength and geometry. Adding a dependence of loop length in addition to the dependence on magnetic field strength improves the correlation of the PFSS and SXT fluxes above that obtained with a parameterization of field strength alone. This additional parameterization of the loop lengths helps to account for contribution to the global signal of the smaller scale, weaker flux outside of the main active regions. We have submitted a paper to the upcoming SPD on these simulations. Klimchuk is writing up his work on coronal heating scaling laws, which he will submit shortly to the Astrophysical Journal. Page 15 Work continues on comparing time series of SXT full disk fluxes with BCS S XV fluxes and GOES fluxes. A time series of daily background fluxes in S XV is now available and is being compared with the SXT fluxes. All the GOES 1 min and 5 min data have been transferred to the NRL computers and is work is beginning to develop a time series of GOES background measurements for the time period of the Yohkoh mission. =========================================================================== University of New Hampshire Activity Report for February 1999-March 1999 =========================================================================== (T. Forbes) An ApJ paper discussing reconnection and CME's has been completed: The Effects of Reconnection on the CME Process, J. Lin and T.G. Forbes The paper contains a section which suggests an explanation for the peculiar motion of the giant X-ray arches reported by Z. Svestka et al. using data from the Yohkoh SXT (1997, Solar Phys. 176, 355-371). They found that, although the arches are similar in many respects to 'post'-flare loops, their upward motion is different. Instead of continually slowing with time, they move upward at a rate which increase with time. My co-author and I show how the difference in behavior can be explained by the increase in the Alfven speed at heights above about 10**5 km when it is incorporated into the standard reconnection model for flare loops. ======================================================================= University Of California Activity Report for February 1999-March 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. Griffiths, Fisher, and Woods have been working 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, allows us to to characterize the differential emission measure distribution, density distribution, and ``filling factor'' for the emitting material in this small active region. A paper describing this work is nearly completed. 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 Martin ATC) have succeeded in modifying the Page 16 existing data analysis software to interactively correct poor vector magnetogram positions which are recorded in the magnetogram database. All of the relevant SFD data has now been extracted from the Lockheed Jukebox system and is stored on disk at Berkeley. Fisher and Chris Johns-Krull (also at SSL/UCB) traveled to Big Bear Solar Observatory (BBSO) March 1-5 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 observing a flare on March 5, 1999 that overlapped with Yohkoh coverage. The flare occurred in NOAA 8477 and was a C3.8 flare at maximum, occurring at 19:25 UT. McTiernan has done a preliminary analysis of the HXT and SXT data from that flare, and finds significant hard X-ray emission, making this a good candidate to test the Halpha linear polarization data for a flare signal, indicating the presence of proton beams. Noise levels in the polarization data are roughly 1%. During the next 1-2 months Johns-Krull and Fisher will carefully examine the polarization data to see if a real signal was detected. 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 April 1999 March 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 March 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