Page 1 PROGRESS REPORT THE SOLAR-A SOFT X-RAY TELESCOPE (SXT) PROGRAM (CONTRACT NAS8-00119) (for March 2001) OVERVIEW The YOHKOH Mission is a program of the Japanese Institute of Space and Astronautical Science (ISAS) with collaboration by the U. S. National Aeronautics and Space Administration and the U. K. Science and Engineering Research Council. The YOHKOH satellite was launched on 30 August 1991 from Kagoshima Space Center (KSC) in Japan. The purpose of this mission is to study high energy phenomena in solar flares and the Sun's corona. Under an international cooperative agreement, Lockheed Martin, under NASA contract, is providing a scientific investigation using the Soft X-ray Telescope (SXT), one of the primary experiments of the mission. The SXT was developed at the Lockheed Martin Solar and Astrophysics Laboratory in cooperation with the National Astronomical Observatory of Japan, and the Institute for Astronomy of the University of Tokyo. MAJOR PROGRAMMATIC ACTIVITIES IN THE MONTH The primary current emphasis is on the Senior Review which requires a written input in May and an oral presentation in July. All of the other programmatic issues are normal and the instrument continues to perform in a satisfactory manner. SOLAR ACTIVITY In early March, solar activity was very low with only four flares above the M1 level. The GOES background level fluctuated between B3 and C1. Prominent non-polar coronal holes were seen first in the southern hemisphere and then in the northern hemisphere. Many eruptions were observed, whose appearances reminded us that they intrinsically had 3-d structures and trajectories. In mid-March, the X-ray background slightly decreased, and no flares above M-class occurred. There was a pair of regions AR 9373 and AR 9384 across the equator, and a sigmoidal structure was seen for long time to the west of the latter region. This structure transformed to an arcade on 16 March, probably corresponding to one of the halo CMEs observed by LASCO. In late March the spectacular AR9393 rotated onto the disk. The huge spots associated with this active region were visible to the naked eye with an area exceeding 2000 millionths. While exceedingly large, this does not class with the largest sunspots ever observed, however. Since 1900, the largest sunspot observed had an area over 6000 millionths. As we found out in spectacular fashion on April 2, the spot area only has a loose correlation with the magnitude of the flare or coronal mass Page 2 ejection it can produce. A large X1.7 flare on March 29 was responsible for the spectacular aurorae seen all over the world during the magnetic storm of March 31, 2001. The auroras were dramatically visible even in Northern and Southern California. (Note: this flare was not the X20 event which occurred on April 2. That event will be covered in next month's report). CAMPAIGNS We participated in three campaigns - the MEDOC quiet Sun campaign, JOP 137 (Time Variation and dynamics of active region loops II - unsolicited) and JOP 138 (Decimetric storms and Decametric type III bursts). There was a second VLA campaign (JOP 140) to study metric noise storms, and we participated in two of the three runs (on the 18th and 23rd in UT). One more run on the 24th coincided with our spacecraft holiday. We continued to be on the alert for sigmoids as Target Of Opportunity. SCIENCE Aschwanden and Alexander analyzed the evolution of the thermal flare plasma during the 2000-Jul-14, 10 UT, Bastille-Day flare event, using spacecraft data from Yohkoh/HXT, Yohkoh/SXT, GOES, and TRACE. The spatial structure of this double-ribbon flare consisted of a wound arcade with some 100 flare loops which lightened up in a sequential manner from highly-sheared low-lying to less-sheared higher-lying dipolar loops. They reconstructed an instrument-independent average differential emission measure distribution that ranges from 1 MK to 40 MK and peaks at 10.9 MK. They found that the time profiles observed by different instruments peak subsequently over 7 minutes with decreasing temperatures from 30 MK to 1 MK, indicating the systematic cooling of the flare plasma. From these temperature-dependent peak time delays they reconstructed the average plasma cooling function for loops observed near the flare peak time, and found that their temperature decrease is initially controlled by conductive cooling during the first 188 s and then by radiative cooling during the next 592 s. From the radiative cooling phase they inferred an average electron density of 4.2e11 cm**-3, which implies a filling factor near 100% for the brightest observed 23 loops with diameters of about 1.8 Mm that appeared simultaneously during the flare peak time and are fully resolved with TRACE. The total thermal energy of this flare amounts to 2.6e31 erg. PUBLICATIONS Submitted: "Flare Plasma Cooling from 30 MK down to 1 MK modeled from Yohkoh, GOES, and TRACE observations during the Bastille-Day Event (2000 July 14)", by M.J.Aschwanden and D.Alexander, submitted to SOLAR PHYSICS for Special Issue on Bastille Flare. URL="ftp://sag.lmsal.com/pub/aschwand/2001_bastille.ps" Page 3 Homologous Coronal Mass Ejections, Wang, J., Zhang, J., Wang, T., Liu, Y., Nitta, N. V., and Li, Y. 2001, submitted to ApJL "Chromospheric Damping of Alfven Waves", by B. De Pontieu, P.C.H. Martens, and H.S. Hudson, submitted to ApJ. "Origin and Evolution of Filament-Prominence Systems", by Petrus C. Martens and Cornelis Zwaan, submitted to ApJ. Accepted: Nitta, N. V., Sato, J., and Hudson, H. S., "The Physical Nature of the Loop-Top X-Ray Sources in the Gradual Phase of Solar Flares", ApJ, accepted Feb. 2001. Watanabe, T., Sterling, A., Hudson, H., and Harra, L., "Energetics of an Active Region Observed from Helium-Like Sulphur Lines", Solar Phys., accepted Feb. 2001. Moore, R. L., Sterling, A. C., Hudson, H. S., and Lemen, J. R., "Onset of the Magnetic Explosion in Solar Flares and Coronal Mass Ejections", ApJ, accepted Feb. 2001 "Downflows and Structure above LDE Arcades: Possible Signatures of Reconnection?", by D. McKenzie and H. Hudson, to appear in Proceedings of The University of Tokyo Symposium in 2000 on Magnetic Reconnection in Space and Laboratory Plasmas (in press). Published: A Filament-Associated Halo Coronal Mass Ejection, Zhang, J., Wang, J., and Nitta, N. 2001, CJAA, 1, 85. Canfield, R. C., Hudson, H. S., and Pevtsov, A. A., "Sigmoids as Precursors of Solar Eruptions", IEEE Transactions on Plasma Science 28, 1780 (2000). Sturrock, P.A., Weber, M., Wheatland, M.S., & Wolfson, R. 2000, Metastable magnetic configurations and their significance for coronal mass ejections. ApJ 548, 492. 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 138339 accesses and 7418 Mbytes transferred for the SXT website and 257589 accesses and 9249 Mbytes transferred for the YPOP website. Page 4 The Astronomy Picture of the Day (APOD) has two different links to the YPOP pages on March 20. You can see the relevant APOD at http://antwrp.gsfc.nasa.gov/apod/ap010320.html 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 FIL Error 01-Mar-01 Pass 5: 010301-0721 Recovered in the second pass on Mar 2. Page 5 DATA FLOW Month Full Frame Images Observing Region Images Received Lost Received Lost Loss % QT FL Tot Thru Jan-99 596203 220644 2390385 576005 2966390 1067616 26.27 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 6459 1807 35467 12092 47559 13757 22.44 Jun-99 6217 1915 23542 13051 36593 10086 21.61 Jul-99 5591 1745 20409 25747 46156 9670 17.32 Aug-99 6827 2503 21725 23361 45086 11844 20.80 Sep-99 5768 2011 21890 3434 25324 10846 29.99 Oct-99 5768 2308 22994 10487 33481 11517 25.59 Nov-99 7552 3425 20754 18772 39526 11974 23.25 Dec-99 7488 2791 22047 5354 27401 10663 28.01 Jan-00 5426 1736 19802 4040 23842 8958 27.31 Feb-00 6533 2052 21801 7017 28818 8982 23.76 Mar-00 6447 2007 22692 21914 44606 11192 20.06 Apr-00 6412 2100 31195 7214 38409 13438 25.92 May-00 6995 1556 28175 14961 43136 8967 17.21 Jun-00 7043 1722 24413 16369 40782 8690 17.57 Jul-00 6674 1920 23505 31739 55244 10235 15.63 Aug-00 9623 1996 20925 1197 22122 6577 22.92 Sep-00 8835 2240 22233 5764 27997 8307 22.88 Oct-00 6348 1524 23309 6629 29938 7916 20.91 Nov-00 6525 1639 20087 10318 30405 6972 18.65 Dec-00 6585 1918 20718 5422 26140 8071 23.59 Jan-01 5610 1231 20469 3161 23630 7317 23.64 Feb-01 6917 1497 25366 1144 26510 7871 22.89 Mar-01 5364 854 20581 7209 27790 5973 17.69 Total 768461 269881 3005120 858732 3863852 1315924 25.41 Number of Full Frame Images Received: 768461 Number of Observing Region Images Received: 3863852 Total: 4632313 Approximate Number of Shutter Moves/CCD Readouts: 7884639 NOTES: * The loss of images is mainly due to BDR overwrites, but there are also occasional DSN dumps which are lost. * It is common to have observing regions which contain more than 64 lines, which requires multiple exposures to make a single observing region image. This is why the number of shutter moves is larger than the number of images received plus those lost. Page 6 ENGINEERING SUMMARY TABLE Month Avg Dark Level # of Dark Spikes CCD Warmings Front Optical (DN) (e/sec) Over 48 Over 64 High / # Support Trans Temp /Days Temp (%) 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 21.6 N/A Jun-99 59.40 1083.0 230091 42440 22.0 N/A Jul-99 59.78 1097.5 231236 46337 23.8 / 1 20.6 N/A Aug-99 59.39 1083.0 229319 43067 21.7 N/A Sep-99 60.04 1107.3 231585 49084 21.8 N/A Oct-99 59.66 1092.9 229735 45263 22.8 N/A Nov-99 59.90 1102.0 231288 47102 23.0 N/A Dec-99 60.55 1126.3 233523 53920 22.5 / 2 25.3 N/A Jan-00 60.27 1115.9 233820 50214 23.4 N/A Feb-00 60.93 1140.6 235079 56836 23.8 N/A Mar-00 60.72 1132.8 234174 54661 22.9 N/A Apr-00 61.10 1147.0 235252 58348 22.2 N/A May-00 61.00 1143.1 234569 57445 21.2 N/A Jun-00 61.19 1150.3 235622 58946 22.8 N/A Jul-00 61.96 1179.3 238114 66905 19.3 N/A Aug-00 61.27 1153.4 236108 59965 56.9 / 2 21.7 N/A Sep-00 61.08 1146.2 235644 58449 22.1 N/A Oct-00 61.44 1159.5 237142 61667 23.1 N/A Nov-00 60.99 1142.7 235849 57271 24.2 N/A Dec-00 61.59 1165.2 237454 63656 23.8 / 2 21.8 N/A Jan-01 61.64 1167.3 238962 62922 22.2 N/A Feb-01 61.84 1174.6 239218 65324 23.5 N/A Mar-01 61.80 1173.3 238903 64984 23.3 N/A NOTES: * The dark current calculations are using full half resolution 2.668 sec images not taken in during the SAA. The dark current rate assumes a "fat zero" of 30.5 DN and a gain of 100 e/DN. * The entrance filter failure of 13-Nov-92 eliminated the capability of taking optical images, so the optical transmission is not available after Nov-92. It also caused an increase in the dark current signal, however some of the increase shown here is an increase in the readout noise and is not a function of exposure duration. Page 7 PERSONNEL TRAVEL SXT Foreign Travel between 1-FEB-01 and 28-FEB-01 BARTUS 1-FEB-01 * 28-FEB-01 * 28 (total of 28 days) HUDSON 5-FEB-01 16-FEB-01 12 28-FEB-01 28-FEB-01 * 1 (total of 13 days) NITTA 18-FEB-01 28-FEB-01 * 11 (total of 11 days) TAKEDA 1-FEB-01 * 28-FEB-01 * 28 (total of 28 days) ---------------------------------------------------------------- Grand Total of 80 days for 4 people NOTE: The "*" signifies travel that actually ends after 28-FEB-01 SXT Foreign Travel between 1-MAR-01 and 31-MAR-01 BARTUS 1-MAR-01 * 31-MAR-01 * 31 (total of 31 days) HUDSON 1-MAR-01 * 14-MAR-01 14 (total of 14 days) NITTA 1-MAR-01 * 16-MAR-01 16 (total of 16 days) TAKEDA 1-MAR-01 * 31-MAR-01 * 31 (total of 31 days) ---------------------------------------------------------------- Grand Total of 92 days for 4 people NOTE: The "*" signifies travel that actually ends after 31-MAR-01 Respectfully submitted, Thomas R. Metcalf Frank Friedlaender Page 8 ======================================================================= Montana State University Activity Report for February - March 2001 ======================================================================= (D. McKenzie) INTRODUCTION: In addition to research into solar phenomena, our activities during this period included efforts to improve the calibration of the SXT image data, service to the community, public outreach, and preparations for Yohkoh's Tenth Anniversary. RESEARCH: Dick Canfield worked with postdoc Bob Leamon on the interplanetary signatures of eruptions that occurred in Yohkoh X-ray sigmoids. The preliminary finding is that leading polarity properties of the clouds tend not to take on the polarity of the large-scale dipole, unlike magnetic clouds as a whole. Canfield also worked with undergrad Angela Colman to extend their flare study to use higher resolution H-alpha movies, to identify the role of emerging flux in the eruptive events. And Canfield worked with MSU undergrad Yuriko Yamazaki to make CDs of Mees coronagraph prominence eruptions. These data now extend from 1991 to 1998, and Yamazaki has finished her work. The CDs will be sent to Tonooka san at Chiba University, for comparison with SXT images. Canfield and Alisdair Davey (with minor support from David McKenzie) worked together to input SXT catalog information into the MaxMillennium Flare Catalog. Davey also succeeded in placing the mission-long set of SXT de-saturated composite images (SFDs) online at MSU. McKenzie continued his collaboration with members of the SUMER team, particularly Bernhard Kliem and Werner Curdt, on analysis of a C4 flare of 06-Nov-99. He also continued analysis of a particularly well-observed coronal jet from 03-Nov-00. Charles Kankelborg worked on field line modeling, via "fluxons". In conjunction with this, Craig DeForest visited the group for a week to work with Charles. Together, they presented a seminar to the MSU group about fluxon modeling, and about their promising progress. With Kankelborg, grad student Becca McMullen is continuing to make progress with loop modeling, and will begin testing alternative heating profiles for the X-ray Bright Point analyzed by Kankelborg & Longcope (1999 Sol Phys 190:59). In research related to calibration of SXT images, Loren Acton has concentrated on attempts to characterize the X-ray scattering properties of the SXT by analysis of starburst images. Some progress has been made (Acton wrote and rewrote a program, starburst_finder.pro, to search the entire SXT SFR database for starbursts by looking at the GOES level at the times of FFIs). Additionally, Acton worked 2 days at Lockheed with Page 9 Phil Shirts, Tom Metcalf, and Sam Freeland on issues related to generation of synthetic SFC leak images. On average these are already a great improvement over the use of terminator SFCs for leak correction. However, there are systematic imperfections that may be improved still further. McKenzie dedicated time to deconvolution of SXT images, using an FFT-based algorithm to remove the effects of photon scattering from the images. The report of this work, undertaken with Metcalf, Shirts, and Acton, is online at http://solar.physics.montana.edu/SXT/Decon2001/dmck_PSF_report.html. In summary, deconvolution can be made to work, with careful choice of the point spread function. McKenzie also continued work with undergrad Shaun Ceci towards a ray trace of SXT. In February and March, Piet Martens continued work on a program for Blind Iterative Deconvolution of SXT PFI's. Again, the objective is to compensate for the point spread function of the instrument. Progress is good, but the task is bigger than was expected. SERVICE: March began with Acton at NSO-Sacramento Peak for an AURA Solar Observatories Council meeting. Canfield worked with Acton and McKenzie on a one-page photo plus caption on the sigmoid-to-arcade pattern, for OMB. The new version of Alphonse Sterling's classic image is at: http://solar.physics.montana.edu/mckenzie/Images/sig2arcade_redux.html McKenzie gave a colloquium to the Physics Department at the University of Nevada - Las Vegas, on the Sun and solar activity. Martens refereed proposals for the Dutch Organization for Pure Scientific Research. Canfield refereed a paper for Astrophysical Journal. OUTREACH and WEB PRESENCE: Canfield and McKenzie worked with Hugh Hudson and Nariaki Nitta to redo the SXT Nuggets for a contribution to the CD that will accompany Solar Physics volume 200. Canfield reformatted the SXT Chief Observer's weekly reports at http://solar.physics.montana.edu/nuggets/ and mirror sites at Lockheed Martin, ISAS, and MSSL. McKenzie maintained the Yohkoh SXT website, which is now online at http://solar.physics.montana.edu/SXT/ with mirror sites at Lockheed Martin and ISAS. McKenzie updated the website for the SXT Deconvolution mini-workshop, which was held in Hawaii at the IfA, January 18-19. The webpage for that CDAW is held at http://solar.physics.montana.edu/SXT/Decon2001/ Page 10 PUBLICATIONS: - Submitted: "Chromospheric Damping of Alfven Waves", by B. De Pontieu, P.C.H. Martens, and H.S. Hudson, submitted to ApJ. "Origin and Evolution of Filament-Prominence Systems", by Petrus C. Martens and Cornelis Zwaan, submitted to ApJ. - Accepted: "Downflows and Structure above LDE Arcades: Possible Signatures of Reconnection?", by D. McKenzie and H. Hudson, to appear in Proceedings of The University of Tokyo Symposium in 2000 on Magnetic Reconnection in Space and Laboratory Plasmas (in press). - Meeting presentation: "Nulls in the coronal magnetic field", by Dana Longcope and Petrus Martens, was presented at the meeting "High-Resolution Solar Magnetography from Space: Beyond Solar-B", in Huntsville, AL, 3-5 April 2001. YOHKOH 10th ANNIVERSARY: Acton and Martens took over as SOC co-chairmen for the Yohkoh 10th Anniversary meeting. Other members of the organizing committee are Becca McMullen, Elizabeth Noonan (grad students), and Jana Halvorson (hired gun). Davey worked on the back end processing of the on-line registration and abstract submission forms. Everything seems on track, with the venue selected, sponsors sending in checks, and the website now open. MISCELLANEOUS: The MSU solar physics group performed the search to hire a new person to serve as SXT Chief Observer, replacing Brian Handy. We have extended an offer. Martens headed up the selection of students for our summer Research Experiences for Undergraduates (REU) project. Five students were selected, to work with Canfield, Kankelborg, Longcope, Martens, and McKenzie. Page 11 ============================================================= Univ of Hawaii Activity Report for February - March 2001 ============================================================= (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 G. Nitta at Mees and LaBonte and Li in Manoa. Our colleagues Kupke 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 poor during these months. Observations were obtained on 70% of all scheduled days. Total coverage was limited by the number of holidays and vacations. The Sun was inactive for much of this time, but the region AR9393 at the end of March signaled a higher activity level. During the last week of March Mees observed 2 M-class flares in this region, and hope for more. LaBonte is processing vector magnetic movies from the IVM for several projects by SXT team members. The newly developed analysis codes provide significant improvements in accuracy in the field determination. Li is completing her analysis of polar coronal streamers to isolate the active regions that contribute to their development. This will permit accurate identification of the sequence of events that cause the corona to become enhanced over such large distances in latitude. ============================================================ Stanford Univ Activity Report for February - March 2001 ============================================================ (P. A. Sturrock) Peter Sturrock and Mark Weber are continuing to compare SXT data with neutrino data, with the goal of confirming or disproving early claims of association between neutrino flux measurements and various indices of solar activity, including coronal brightness. Massetti and Storini [1996, ApJ 472, 827] carried out tests for correlation between coronal green-line data and Homestake neutrino measurements. We are working with neutrino measurements produced by the GALLEX and GNO experiments, and X-ray flux measurements from SXT. As part of the work for his dissertation, Mark has already compiled time series for the daily mean Page 12 SXT flux for the nine latitude bins, 60S, 45S,..., 45N, 60N. From earlier investigations, we have found evidence that the neutrino flux is modulated by solar rotation. We have therefore conjectured that the correlation, if real, may be due simply to the fact that the two variables (neutrino flux and X-ray flux) are both subject to similar periodic modulations. We have previously reported on our preliminary comparison of the SXT and neutrino rotational modulations. In recent weeks, we have carried out what we consider to be an improved analysis, proceeding as follows: (a) For SXT data for each of the nine latitude bands, we have formed a power spectrum. We have then formed the mean spectrum of these nine spectra. We find that it comprises one dominant peak at 13.48 y^-1, with a half-height half-width of 0.63 y^-1. We regard this mean spectrum as a "template" that we can use to determine whether or not GALLEX-GNO data have a periodicity consistent with the rotational periodicity determined from SXT data. (b) We formed the spectrum of the GALLEX-GNO data, using the Lomb-Scargle method since the timing is irregular. We then formed a weighted integral of this spectrum, using the SXT rotational modulation template as the weighting function. This is a simple and objective way to measure the consistency of the neutrino spectrum with the SXT rotational spectrum. (c) In order to arrive at a robust (model-independent) significance estimate of the result obtained in step (b), we repeated step (b) 10,000 times, shuffling the data each time. By "shuffling" we mean that the flux measurements (but not the start and end times) are randomly re-assigned among runs. In this way, we find that our result from (b) is significant at the 1 percent level, i.e. there is less than 1 percent probability that the correspondence between the SXT and neutrino data is due to chance. We are beginning to consider the implications of the above result, and in particular to consider whether it can help us understand the fact that the corona tends to rotate rigidly rather than differentially. It has been proposed by Stenflo [1977, Astron. Astrophys. 61, 797] that the explanation may be that the large-scale coronal structure is determined by magnetic flux anchored to structures deep in the convection zone. This concept fits well with our result, since the rotation rate in this region (as determined by MDI) is about 14.5 y^-1 (sidereal), i.e. 13.5 y^-1 (synodic), that is completely consistent with the common peak in the SXT and neutrino data sets. Peter and Mark continue to collaborate with Jim McTiernan on the problem of reconstructing coronal magnetic fields from photospheric vector magnetograph data. Jim has reprogrammed in IDL a procedure (the optimization-function procedure) previously developed by George Roumeliotis and Mike Wheatland. This should make it easier for other groups to use this program. Page 13 Peter participated in the workshop "Beyond Solar-B" at Marshall Space Flight Center last week, at which he reviewed several procedures that have been proposed for reconstructing nonlinear force-free fields from vector magnetograph data. As a result of this review, there are two steps that now seem promising: (a) We could examine a procedure, involving irregular time steps, that was proposed by Chodura and Schluter [1981, J. Comp. Phys. 41, 68] for speeding up relaxation procedures such as the magneto-frictional procedure or the optimization-function procedure. (b) We could take a closer look at another procedure proposed by Roumeliotis [1996, ApJ 473, 1095], that he called the "Stress- And-Relax" method. We plan to review these options in the near future. In his investigation of CME energetics and the Aly-Sturrock theorem, Mark has spent some time comparing his solution with previous attempts to model pre-eruptive magnetic field configurations. The most similar research was by Lin et al. [1998, ApJ 504, 1006], who analytically solved for a magnetic torus in the "thin flux-tube" approximation (minor radius much less than major radius). They were unable to produce configurations with sufficient energy to open the overlying dipole field. The toroidal energy is a stronger function of cross-sectional area than of the twist, so unlike our numerical solution, their small tube radius restricted the total energy to be less than the open-field limit of the Aly-Sturrock theorem. Low & Smith [1993, ApJ 410, 412] solved for similar configurations of larger area, but their torus had no azimuthal component, and hence did not model a twisted flux-tube. They further derived the result that *no* equilibrium configuration with dipole boundary conditions can have total energy greater than 120% of the Aly-Sturrock limit. Our solution is consistent with this claim, although it does have energy greater than the Aly-Sturrock limit. It would be interesting to see if the method of Sturrock and Weber can find solutions above the 120% threshold. PUBLICATIONS Sturrock, P.A., Weber, M., Wheatland, M.S., & Wolfson, R. 2000, Metastable magnetic configurations and their significance for coronal mass ejections. ApJ 548, 492. Page 14 =========================================================================== Solar Physics Research Corp. Activity Report for February - March 2001 =========================================================================== (K. Harvey) KAREN L. HARVEY: Activities for February and March: (1) Continued with the analysis of the 18 December 1998 HAO/CHIP He I 10830 data to measure the magnetic flux as a function of time within an area bounded by the two flare ribbons and the polarity inversion separating them and within the associated transient coronal holes and comparison with other data for this event. As mentioned in previous reports, the objective of this study, being done in collaboration with Terry Forbes, is to determine the reconnection rate of a flare. The measurements were made mapping the flare and coronal hole boundaries one the singe NSO/KP full-disk magnetogram for 18 December, assuming that the photospheric field is radial and does not change over the observed during of the flare. The magnetic flux determination within the two coronal holes and flare ribbons is completed. We find that the combined magnetic flux in the flare ribbon and transient coronal hole in the positive flux is equal to that in the unsigned negative polarity. The change in magnetic flux was rapid initially, increasing at a rate of 3.6 x 10^18 Mx/s during the first 20 minutes; the increase slows to a rate of 1.7 x 10^17 Mx/s for the duration of the observations. At the end of the observations, 2139 UT, the total flux involved in the flare and transient coronal holes was 1.6 x 10^22 Mx. These magnetic flux measurements will checked using the MDI magnetograms. The He I 1083 nm observations of the transient coronal holes were compared with the X-ray and EUV images at several temperatures and levels in the solar atmosphere. About six minutes after the coronal holes first appeared in the He~I 1083 nm observations, we find that one of the coronal holes as seen in the EIT Fe~XII 19.5 nm image, as inferred from the developing area of low coronal emission, was smaller in width, but apparently longer than the He I 1083 coronal hole. About one hour after the start of the flare, we find that both of the transient coronal holes are larger in the Fe IX/X 17.1 nm, Fe XII 19.5 nm, Fe XV 28.4 nm images than in the He I 1083 nm line. The difference in the manifestations of the holes between the corona and chromosphere is confirmed by the He II 30.4 nm images. Comparison between the He II 30.4 nm and He I 1083 nm images indicates a good correspondence in the location and extent of the transient coronal holes. We are currently comparing the transient holes in the SXT images with those observed in other images at different temperatures. (2) Continuing with a comparison of the coronal holes identified in Page 15 NSO/KP He I 10830 rotation maps and with corresponding Yohkoh/SXT rotation maps to determine if the structures identified as coronal holes in He I 10830 all are associated with low emission areas. Plans for April and May: Continued analysis and study (1) with T. Forbes of the reconnection rate of magnetic fields during long-duration arcade events/He I 10830 2-ribbon flares associated with X-ray dimmings and transient coronal holes; (2) of the association of coronal holes observed in He I 10830 spectroheliograms and the SXT full-frame images; this includes isolated, non-polar coronal holes, as well as the transient coronal holes; (3) of collected XBP data, looking at the association and timing of XBP with magnetic bipole evolution. HUGH S. HUDSON Activities for February and March Presented a colloquium talk at the Institute for Astronomy (U. Hawaii) entitled "Searching for Solar Shocks." The preparation time for this should have been devoted to writing the paper (see below)! I also attended the final session of the ISSI workshop on subscale structure. This workshop is about nanoflares, really, and the interesting idea I came away with was the concept of "lumpy loops", i.e., the signature that multiple simultaneous nanoflares along a given flux tube (say a TRACE one) might show. Previously many people have concentrated on the temporal variance, occurrence rate, etc., but in fact there ought to be spatial signatures as well. I also gave a lunch talk at Berkeley based on the nuggets compilation and expectations of HESSI. With Canfield, McKenzie, and Nitta, I put together the SXT contribution for the Solar Physics. Vol. 200 CD-ROM issue. This consists of jpeggified science nuggets for the most part. At Dick's suggestion we also incorporated a memorial page in honor of Minoru Oda, who passed away March 1; he was instrumental in Yohkoh development among many other accomplishments. S. Kahler is spending March and April at ISAS, working on coronal hole boundaries - a rich subject indeed, and one for which there has been comparatively little systematic work using Yohkoh images. Plans for April and May: 1. Continue to work on large-scale waves with Joe Khan. 2. Participate in ISSI workshop on flares (P. Cargill, convener). My particular homework problem is the subject of the "number problem" for fast electrons in solar flares. This concerns the lack of sufficient numbers of electrons in the flaring corona to explain the hard X-ray emission - it is a long-standing problem for some models. Page 16 3. Work on Bastille Day ribbons (with L. Fletcher) for the Solar Physics special issue and for the SPD meeting. http://solar.physics.montana.edu/SXT/Decon2001/). 4. Wait for HESSI to be launched. PUBLICATIONS Papers published: Canfield, R. C., Hudson, H. S., and Pevtsov, A. A., "Sigmoids as Precursors of Solar Eruptions", IEEE Transactions on Plasma Science 28, 1780 (2000). Papers Accepted: Nitta, N. V., Sato, J., and Hudson, H. S., "The Physical Nature of the Loop-Top X-Ray Sources in the Gradual Phase of Solar Flares", ApJ, accepted Feb. 2001. Watanabe, T., Sterling, A., Hudson, H., and Harra, L., "Energetics of an Active Region Observed from Helium-Like Sulphur Lines", Solar Phys., accepted Feb. 2001. Moore, R. L., Sterling, A. C., Hudson, H. S., and Lemen, J. R., "Onset of the Magnetic Explosion in Solar Flares and Coronal Mass Ejections", ApJ, accepted Feb. 2001 TAKEDA AKI: Activities for February and March: I worked for three full weeks in total as an SXT_CO as below. They are less than those in the previous report since there were sufficient number of SXT_COs at ISAS for these months. week 05 (29-Jan through 4-Feb): SXT_CO (full week) week 11 (12-Mar through 18-Mar): SXT_CO (1/3 week, shared with N. Nitta) week 12 (19-Mar through 25-Mar): SXT_CO (full week) week 13 (26-Mar through 1-Apr): SXT_CO (2/3 week, shared with H. Hudson) As an sxt_co of week 05, I completed my second 'science nugget', in which I described a filament eruption observed on 26th January. It was an interesting event, since there was little or no enhancement in soft X-ray flux (GOES, SXT), but there was a significant ejection of coronal mass observed with SoHO/LASCO. http://isass1.solar.isas.ac.jp/nuggets/2001/010202/010202.html Page 17 In February, I took the initiative to reconsider the requested cadence of the 30sec exposure images, which we have taken for many years for the study of XBPs. Although these longer exposure images are important to detect faint XBPs, they may degrade CCD especially in this maximum phase of solar activity. After discussing with the campaign leaders, we set a new policy: We will take those images at weekly base, at least, like dark or diffuser calibrations, unless the activity is very high. There was an SXT error on 1-Mar associated with the DP error found one orbit earlier. I analyzed the SXT behaviour and found the malfunction in exposure system. For the frames with DPE greater than 19, actual exposure time was significantly lower than expected. I have already reported this at an operation meeting, but the cause of this strange behaviour is still unknown. Since last December, we SXT_COs have participated in the sigmoid campaign as a target of opportunity. We are responsible for sending out a notice of finding a sigmoid which deserve to be observed. While I was a CO, I found two good sigmoid and tried to send the notice, but failed both times. In the first trial, I sent it not from sxt_co's address, but my personal address which is not authorized so that it could not reach the participants properly. In the second, there was another promising region near the sigmoid, and thus I did not clearly declare the start of the campaign. This, as a result, caused some confusion among the participants. With an effort of R. Canfield, a brief manual is prepared now. So, I would never like to miss the next opportunity. In the remaining weeks when I was free from the CO's task, I spent most of my time analyzing SXT and SoHO/EIT images taken around the solar total eclipse in 1999. I attended two meetings (2/23-24 at National Astronomical Observatory, Japan, and on 3/28 at a spring meeting of Astronomical Society of Japan) and made a presentation based on this analysis. JANOS BARTUS Activities for February and March: We set the new isass0 and isass1 servers to work. They offer considerably higher performances by the faster CPUs, larger and faster hardisks as well as the Linux OS. The multiple levels of redundancy provides enhanced reliability against system crashes. The new servers are being connected and sharing a part of their file system via our Gb/s fiber optic private network. The Linux operating system means vendor independent, free and easy upgrade. Also future hardware upgrades will be cheaper and easier compared to buying new WS's from Compaq or Sun. Additional works: - linux support for Philips webcamera, video conferencing facility will be available soon for isass0/1 between remote linux-linux or Page 18 linux-windows computers - X server updates on isass0/1 - kernel reconfiguration - software debuggings - mirror software upgrade - Yohkoh archive CD creation and distribution - keep running the reformatting on isass5 - daily sysadmin tasks - continuous monitoring of the system state and availability (from home too even in the weekends) Plans for April and May: - isass5 OS upgrade to Linux or exchange isass5 with a Linux PC - pollux OS upgrade - connect all the Lockheed computers within ISAS into our new Gb fiber optic network. ======================================================================= University Of California Activity Report for February - March 2001 ======================================================================= (G. Fisher) Acton (MSU), Fisher, and Metcalf have discovered that the X-ray Luminosities found in Fisher et al. ApJ 508 885 (1998) are all too high by a factor of 4, given the assumptions that were made in that paper. While the correlation studies in that paper remain unchanged, the numerical values of the X-ray radiance needs to be reduced by a factor of 4. These values are being used in a study being carried out by Pevtsov (NSO), studying the dynamic range of the relationship between magnetic flux and X-ray luminosity ranging from quiet Sun conditions to very magnetic pre-main sequence stars. Johns-Krull (UCB) is continuing his work on the analysis of H alpha linear polarization data taken during solar flares, with an emphasis on comparison with SXT and HXT data. The data have been taken by Johns-Krull and Fisher over the past several years at BBSO. H alpha linear polarization is predicted to be a signature of proton beams impinging on the solar chromosphere during flares. Thus far, no detectable levels of polarization have been seen with observed limits of roughly 1%. Johns-Krull has started working on a draft of a paper to be submitted to Solar Physics describing this work, and has given 2 colloquia on the subject during the past couple of months, at BBSO and NJIT. Page 19 ------------------------------------------------------------------------------- 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 2001 March 2001 |------------------------------- | 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 - 00119 -----------------------------------------------|------------------------------- 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 2001 |------------------------------- |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 | 19 | ------------------------|------------------------|-----------------|-----------