Page 1 PROGRESS REPORT THE SOLAR-A SOFT X-RAY TELESCOPE (SXT) PROGRAM (CONTRACT NAS8-40801) (for March 2000) 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 major activities continued to include finishing the proposal for the continuation of mission operations and data analysis and the receipt of management approval for submittal. The proposal was sent to NASA on April 6, 2000. SOLAR ACTIVITY In early March, Solar activity was moderate. An X1.1 flare occurred on 02-Mar in NOAA 8882, where several other flares were also reported. Baseline solar activity stayed above C-level until the middle of the month, then dropped back to below C from the 9th onwards. In mid-March, GOES X-ray levels picked up slightly and stayed around C1 level. There were 5 M class flares, the largest being an M2.1 flare with peak around 21:00 18-Mar-00. In late March, Yohkoh missed two X-class flares on 22 March and 24 March 2000. Both occurred at night with the second flare almost completely coinciding with Yohkoh night (07:30-08:05 UT), followed by SAA (07:56-08:12 UT). The GOES X-ray level stayed around C2. As March ended activity shot upwards - 9 M flares in 2 days - and then shot downwards just as fast. Overall, March was the most active month so far in this cycle. Solar activity was moderate to high - 30 M flares and two X flares. Predictions of this activity seemed to have missed in both directions, the subject of the science nugget for March 24 (http://www.lmsal.com/YPOP/Nuggets). In the selected active region for Page 2 Max Millennium campaign #6, we noted that the flares initially did not seem eruptive. This changed with time. The AR structure did not show a clearly-defined coronal sigmoid, and instead consisted of multiple loops. CAMPAIGNS SXT led and participated in Max Millennium campaign #6, which was a joint campaign with the IVM at Mees, BBSO and TRACE, with the primary goal of making a confident identification of an H alpha line polarization signature during a solar flare. Two X-flares occurred during the campaign, but neither Yohkoh nor the ground-based observatories were able to observe these flares. However, the IVM at Mees Observatory observed a total of 31 C, M, and X class flares. A summary events list is on their campaigns page at http://www.solar.ifa.hawaii.edu/Campaigns/maxmill_op006.html. All in all the Max Millennium campaign proceeded auspiciously, with the probable successful joint observation of many flares in AR 8906. The TRACE data apparently will be the definitive dataset on UV behavior at high resolution and frequent sampling, and we had some flares strong enough to give Yohkoh HXT high time resolution, including examples of the wide-separation hard-spectrum footpoint morphology. Among the ground-based observations, there are some H-alpha observations from Big Bear with ultra-high time resolution. Yohkoh commenced support of VLA observations and of JOP083 at the end of the month. We have instituted a scheme by which the SXT chief observers will keep a watch out for interesting developments of various types. There is a Web page with details at http://isass1.solar.isas.ac.jp/sxt_co/alerts.html for those interested. We're doing this because the SXT chief observers don't rotate so frequently, helping the attention span, and because some solar features are seen first and best in the SXT data. SCIENCE Aschwanden and Nitta investigated the effect of hydrostatic scale heights in coronal loops on the determination of the vertical temperature structure of the corona. Every method that determines an average temperature at a particular line-of-sight from optically thin emission (e.g. in EUV or soft X-ray wavelengths) of a multi-temperature plasma, is subject to the emission measure-weighted contributions from different temperatures. Because most of the coronal structures (along open or closed field lines) are close to hydrostatic equilibrium, the hydrostatic temperature scale height introduces a height-dependent weighting function that causes a systematic bias in the determination of the temperature structure as function of altitude. The net effect is that the averaged temperature seems to increase with altitude, even if every coronal loop (of a multi-temperature ensemble) is isothermal in itself. They simulated this effect with differential emission measure distributions observed by SERTS and Yohkoh/SXT and find an apparent Page 3 temperature increase due to hydrostatic weighting. This effect largely explains the systematic temperature increase in the upper corona reported in recent studies (e.g. by Sturrock et al., Wheatland et al., or Priest et al.), rather than being an intrinsic signature of a coronal heating mechanism. Hudson analyzed a "sympathetic flare", one resulting from a perturbation caused by another flare. On March 2 SXT observed the second X-class flare of the year 2000, and it displayed powerful ejecta that clearly perturbed some, but not all, nearby structures. A powerful flare such as this behaves in some ways like a magnetic explosion. This one was no exception, with successive ejection of fragmented and loop-like structures in a direction roughly consistent with the local solar vertical. The flare core was amazingly compact, as is often the case for these very impulsive events, and had a density approaching 10^12/cm^3. The sympathetic event flares up and bends as though to follow the blast emanating from the flare core. But other features at comparable distances show no effect. This is typical behavior for a flare; catastrophic changes in the emitting material, and often no dynamics at all in nearby features. From this one concludes that some parts of these regions must have much higher magnetic pressure than gas pressure. (see http://www.lmsal.com/YPOP/Nuggets/2000/000303/000303.html) PUBLICATIONS Submitted: Aschwanden,M.J., Nightingale,R.W., Alexander,D., Reale,F., and Peres,G. 2000, ApJ, Evidence for Nonuniform Heating of Coronal Loops Inferred from Multi-Thread Modeling of TRACE Data Aschwanden,M.J. and Nitta,N. 2000, ApJ Lett., The Effect of Hydrostatic Weighting on the Vertical Temperature Structure of the Solar Corona "Detection of Coronal Dimming in Microwaves", N. Gopalswamy, Y. Hanaoka, and H. Hudson (ApJ, 2000) McKenzie, D. E "Supra-arcade Downflows in Long-Duration Solar Flare Events", 2000, Solar Physics. Sturrock, P.A., Wheatland, M.S., & Wolfson, R. 2000, Metastable magnetic configurations and their significance for coronal mass ejections. Ap J. Wheatland, M.S., Sturrock, P.A., & Roumeliotis, G. 1999, An optimization approach to reconstructing force-free fields, ApJ. Accepted: Canfield, R. C., Hudson, H.S., and Pevtsov, A. A. ``Sigmoids as Precursors of Solar Eruptions'', Invited Paper for ``Special Issue of IEEE Transactions on Plasma Science, 2000'', 2000. Page 4 S.D. Bao, A.A. Pevtsov, T.J. Wang and H.Q. Zhang: 2000, "Helicity Computation Using Observations From Two Different Polarimetric Instruments", Solar Physics Canfield, R. C., Hudson, H.S., and Pevtsov, A. A. ``Sigmoids as Precursors of Solar Eruptions'', Invited Paper for ``Special Issue of IEEE Transactions on Plasma Science, 2000'', 2000. B. Schmieder et al., "Dynamics in Restructuring Active Regions Observed during SoHO/Yohkoh/GBO Campaigns", 2000, Adv. Space Res. 2000, 25(9), 1879. Background Solar Corona Revealed by Time Series Observations, Jing Li, J. Kuhn, B. LaBonte, J. C. Raymond, and L. W. Acton, 2000, ApJ, in press. Jovian X-ray Emission from Solar X-ray Scattering, A. Maurellis, T. E. Cravens, G. R. Gladstone, L. W. Acton, 2000, Geophys. Res. Letters, in press. A Method to Determine the Heating Mechanisms of the Solar Corona, E.R. Priest, C.R. Foley, J. Heyvaerts, T.D. Arber, D. Mackay, J. L. Culhane, and L.W. Acton, 2000, ApJ., in press. Roald, C.B., Sturrock, P.A., & Wolfson, R. 1999, The dependence of coronal heating on magnetic flux density in the photosphere, Ap J, in press. Wolfson, R., Roald, C.P., Sturrock, P.A., and Weber, M. 1999, Coronal X-ray brightness and photospheric magnetic field: A study in correlations, ApJ, in press Published: A. A. Pevtsov: 2000, "Transequatorial Loops in the Solar Corona", Astrophys. Journal, 531, 553-560. "Coronal Magnetic Implosions": H. S. Hudson, ApJ 531, L75 (2000). "Coronal Magnetic Implosions": Yohkoh 8th anniversary symposium proceedings (extended abstract) 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 198781 accesses and 8394 Mbytes transferred. Page 5 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: ** No errors reported this month ** Page 6 DATA FLOW Month Full Frame Images Observing Region Images Received Lost Received Lost Loss % QT FL Tot Thru Jan-98 519090 199670 2104062 430632 2534694 954257 27.08 Feb-98 6606 1644 25257 3606 28863 8989 23.75 Mar-98 6043 2056 23029 10399 33428 10939 24.66 Apr-98 6537 1103 22656 8087 30743 6339 17.09 May-98 7569 1838 28292 19018 47310 9868 17.26 Jun-98 6463 1638 24990 5618 30608 9051 22.82 Jul-98 6810 1892 27046 7357 34403 9970 22.47 Aug-98 5823 1960 22978 14126 37104 11167 23.13 Sep-98 6776 1432 21814 11626 33440 7753 18.82 Oct-98 6573 1901 23520 5198 28718 9220 24.30 Nov-98 6442 1695 25124 26948 52072 9920 16.00 Dec-98 5962 2005 21490 15770 37260 10561 22.08 Jan-99 5494 1825 20087 17620 37707 9622 20.33 Feb-99 5729 1525 30802 9798 40600 10630 20.75 Mar-99 6807 1844 24721 12354 37075 10064 21.35 Apr-99 6715 1371 25113 4179 29292 7791 21.01 May-99 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 2202 817 8072 5606 13678 4261 23.75 Total 681270 248509 2709484 731297 3440781 1208699 26.00 Number of Full Frame Images Received: 681270 Number of Observing Region Images Received: 3440781 Total: 4122051 Approximate Number of Shutter Moves/CCD Readouts: 7042652 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 7 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-98 55.94 953.7 209254 22122 23.8 / 2 22.6 N/A Mar-98 56.29 966.6 213519 23249 21.8 N/A Apr-98 56.44 972.1 214676 23890 20.8 N/A May-98 56.90 989.4 215651 26905 21.4 N/A Jun-98 57.11 997.5 216285 28223 20.1 N/A Jul-98 57.01 993.7 215499 27493 21.4 N/A Aug-98 57.36 1006.7 217355 29544 20.9 N/A Sep-98 57.43 1009.5 218520 29683 20.9 N/A Oct-98 57.59 1015.3 220504 30221 21.3 N/A Nov-98 58.17 1037.0 223755 34614 22.5 / 2 23.4 N/A Dec-98 57.86 1025.5 221918 32420 23.8 N/A Jan-99 58.74 1058.6 227503 38238 23.1 N/A Feb-99 58.44 1047.4 224002 36198 23.2 N/A Mar-99 59.26 1078.1 227900 43051 21.7 N/A Apr-99 58.82 1061.4 225973 38963 23.8 / 1 21.4 N/A May-99 58.68 1056.4 225385 37726 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 60.22 1114.0 232439 49840 23.0 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 8 PERSONNEL TRAVEL SXT Foreign Travel between 1-MAR-00 and 31-MAR-00 ACTON 26-MAR-00 31-MAR-00 * 6 (total of 6 days) FLETCHER 5-MAR-00 25-MAR-00 21 (total of 21 days) HUDSON 1-MAR-00 * 4-MAR-00 4 10-MAR-00 22-MAR-00 13 31-MAR-00 31-MAR-00 * 1 (total of 18 days) MCKENZIE 1-MAR-00 * 6-MAR-00 6 (total of 6 days) NITTA 12-MAR-00 29-MAR-00 18 (total of 18 days) SHIRTS 1-MAR-00 * 6-MAR-00 6 (total of 6 days) ---------------------------------------------------------------- Grand Total of 75 days for 6 people NOTE: The "*" signifies travel that actually ends after 31-MAR-00 SXT Foreign Travel between 1-APR-00 and 30-APR-00 ACTON 1-APR-00 * 22-APR-00 22 (total of 22 days) HANDY 15-APR-00 30-APR-00 * 16 (total of 16 days) HUDSON 1-APR-00 * 30-APR-00 * 30 (total of 30 days) ---------------------------------------------------------------- Grand Total of 68 days for 3 people NOTE: The "*" signifies travel that actually ends after 30-APR-00 Respectfully submitted, Thomas R. Metcalf Frank Friedlaender Page 9 7 ================================================================= Montana State Univ Activity Report for February and March 2000 ================================================================= (B. Handy) OPERATIONS Canfield served as Yohkoh Duty Scientist at Mees Solar Observatory the first week of March. Handy spent the month of February at the Yamasa Language Institute in Okazaki, Japan, in preparation for a larger role in SXT operations. McKenzie spent February at ISAS, serving as SXT Chief Observer. While there, he redefined the Yohkoh normal pointing (Hudson's suggestion), to aim the telescope about 1 arcminute further west. Aside from some erratic scheduling due to events surrounding Astro-E and an interesting Leap Year-related software bug, there were no special operations. Davey provided computer support for the solar group, with activities involving systems upgrades, performance and security issues. He reconstructed the RAID array server SXT4 which is now being used for reproduction of SSCs for the new Yohkoh Movie. MEETINGS McKenzie and Longcope attended the meeting "Magnetic Reconnection in Space and Laboratory Plasmas" at the University of Tokyo, February 29 through March 4. He presented a talk on supra-arcade downflows (H. Hudson co-author), and a poster on hard X-rays from slow LDEs (H. Hudson lead author). Pevtsov Attended "International Conference on Solar Eruptive Events", The Catholic University of America (March 6-9) and presented a poster paper "On the role of chirality of solar magnetic fields in geomagnetic events". Canfield participated in the meeting "Origins, Development and Effects of Coronal Mass Ejections" at Elmau, Germany, 27 March - 1 April 2000. He presented a preliminary interpretation of the sigmoids study discussed above. RESEARCH Acton continued to work on the new Yohkoh/SXT science movie and SXT calibration. This will be his primary activity during the month of April while in attendance at ISAS. He prepared some 1998 x-ray irradiance data for Swamanithan at JHU Applied Physics Lab, who is looking at x-rays and atmospheric NO balance again. He also started a collaboration with Aschwanden on coronal temperature structure based upon Page 10 the August 1992 long-exposure SXT offpoints. Canfield worked with Zarro, Nitta and Qiu on the co-aligned images for the Whole Sun Month 3 Flare Topology Working Group study of flares in sigmoidal AR 8668. Canfield studied the co-aligned SXT, TRACE, SoHO, BSO, and SOON movies for the Whole Sun Month 3 Flare Topology Working Group study of flares in sigmoidal AR 8668. He compared the movies with the topological model of Titov and Demoulin (A&A 1999). At this point the study is at the "striking similarities and intriguing differences stage. Canfield worked with various students on the analysis of SXT and MCCD data. Trish Van Lew studied SXT jet / MCCD surge events using the Blehm/Pevtsov list of jets and surges inferred from SXT sfd files throughout the mission to date. Angela Colman studied tether-cutting events similar to those observed by Canfield et al before the Nov 15 1991 event. Yuriko Yamazaki (ACE Language Institute) and Eric Erickson, and Tyler Bangs (Headwaters Academy) studied the relationship between sigmoids and signatures of eruptions in the SXT sfd movies on videodisk. Davey started work on further characterizing SXT point spread function. He has also nearly completed a redesign of the Max Millennium Preprint Archive software, and started training a new assistant for Unix system support. Kankelborg completed the first draft of loop topology paper with P. Martens as co-author. He also worked on a new method to model nonlinear force free fields. A first whack at coding the algorithm in IDL produced a pretty picture of a uniformly twisted coronal loop. These results have not yet been proven to be solutions of JxB=0, but this does not dampen his enthusiasm. McKenzie did preliminary analysis of a C flare from November 1999, in collaboration with Werner Curdt. This was part of JOP 104; SUMER has high cadence spectra, SXT has mediocre temporal coverage but sees some loop expansions and faint ejecta nevertheless. Martens collaborated with N. Nitta on hot and cool loop studies (SXT & TRACE). He also worked on a paper on prominences (with the late Kees Zwaan as co-author), still not completed. Also worked a bit with Mark Weber on a rewrite/extension of our paper on axial fields in prominences. Pevtsov continued to work with Loren Acton on study luminosity of quiet corona, and did substantial data reduction (MSFC, ASP) for projects with Mona Hagyard and Dana Longcope. He finished writing a paper on "Coronal Structures as Tracers of Sub-Surface Processes" based on an invited talk given at IAU 179 colloquium. Page 11 OUTREACH Acton gave a couple of school programs and was interviewed for the planetarium show on the sun that is being produced at the Museum of the Rockies. Acton also attended the World Water Forum in The Hague, Netherlands. Canfield reformatted the SXT Chief Observer's weekly reports at http://solar.physics.montana.edu/nuggets/ and mirror sites at Lockheed, ISAS, and MSSL. He gave the featured talk at the annual Montana Astrofair at the Museum of the Rockies: "Solar Max 2000: What and When?", and chaired the search committee for the new experimental space physicist faculty position. He served on Meredith Wills-Davey's graduate committee. Meanwhile, he worked with Jim Manning and others on the solar planetarium show for the Museum of the Rockies. Canfield chaired the search committee for the new experimental space physicist faculty position. Canfield, Longcope and Martens also worked with Jim Manning and others on the solar planetarium show for the Museum of the Rockies. Brian Handy gave a talk in Pigeon Japanese on SXT and TRACE at the Yamasa Language Institute in Okazaki, Japan. On March 28th Handy, Kankelborg, and Martens presented the Webcast lecture on "Mission Operations" for the "Space Mission Design Seminar" of the Upper Midwest Aerospace Consortium. It was broadcasted to universities in North and South Dakota, Wyoming, Montana, and Idaho -- a lot of land, but few people..... It became evident once more that solar imagery fascinates non-solar scientists and students. On March 22, P. Martens hosted Prof. Bob Twiggs from Stanford University's Space System's Development Lab. He gave two inspiring seminars at MSU on their small student-built (= low-cost) satellites for space applications program. HONORS L. Acton will be awarded an honorary D.Sc. in May from the University of Colorado-Boulder. Acton was also the recipient of the Year 2000 Hale Prize. PUBLICATIONS Papers Submitted: ----------------- McKenzie, D. E "Supra-arcade Downflows in Long-Duration Solar Flare Events", 2000, Solar Physics. Page 12 Proceedings of IAU 195 have been submitted to the ASP editor for final review (Martens, Tsuruta, and Weber, eds.). Papers Accepted: ---------------- Canfield, R. C., Hudson, H.S., and Pevtsov, A. A. ``Sigmoids as Precursors of Solar Eruptions'', Invited Paper for ``Special Issue of IEEE Transactions on Plasma Science, 2000'', 2000. B. Schmieder et al., "Dynamics in Restructuring Active Regions Observed during SoHO/Yohkoh/GBO Campaigns", 2000, Adv. Space Res. 2000, 25(9), 1879. A. A. Pevtsov: 2000, "Transequatorial Loops in the Solar Corona", Astrophys. Journal, 531, 553-560. S.D. Bao, A.A. Pevtsov, T.J. Wang and H.Q. Zhang: 2000, "Helicity Computation Using Observations From Two Different Polarimetric Instruments", Solar Physics "Background Solar Corona Revealed by Time Series Observations", Jing Li, J. Kuhn, B. LaBonte, J. C. Raymond, and L. W. Acton, 2000, ApJ, in press. "Jovian X-ray Emission from Solar X-ray Scattering", A. Maurellis, T. E. Cravens, G. R. Gladstone, L. W. Acton, 2000, Geophys. Res. Letters, in press. "A Method to Determine the Heating Mechanisms of the Solar Corona, E.R. Priest, C.R. Foley, J. Heyvaerts, T.D. Arber, D. Mackay, J. L. Culhane, and L.W. Acton, 2000, ApJ., in press. ============================================================= Univ of Hawaii Activity Report for February and March 2000 ============================================================= (B. LaBonte) Our activities included support of Yohkoh operations and data analysis at ISAS, coordinated ground-based data acquisition (including designated Yohkoh campaigns) at Mees, collaborative analysis of Yohkoh/Mees data, and preparation of manuscripts. Operational support for SXT was provided by Nitta at Mees and LaBonte and Li in Manoa. Our colleagues Kupke and Mickey at Manoa, Canfield at Montana State University, Wuelser and Metcalf at Lockheed, and Hudson at Solar Physics Research Corporation aided in advice and oversight of Mees operations. Weather at Mees was generally good, with some observations obtained on 86% of all possible days. Page 13 Mees observations supported the Max Millennium Campaign, H-alpha Linear Polarization in Flares campaign to the extent that weather and instruments permitted. Mickey and Li traveled to Mees to extend the observing days. Although the second week of the campaign had poor weather, a total of 31 C, M, and X class flares were observed. A summary events list is on our campaigns page at http://www.solar.ifa.hawaii.edu/Campaigns/maxmill_op006.html. In support of the campaign, we generated both continuum and H-alpha line center quicklook movies of the target region. We also have a new tool that generates a quicklook movie from the full disk MWLT images showing the largest spot regions; this is useful for planning, in identifying which regions are most rapidly evolving. All movies are linked on our latest images page, http://www.solar.ifa.hawaii.edu/Daily/mees_obs.html. LaBonte has developed a new procedure for deriving magnetic fields from Stokes spectra from the Mees Imaging Vector Magnetograph. It avoids saturation and stray light effects in sunspots. Reanalysis of observations in support of the Whole Sun Month 3 Sigmoids campaign is now in progress. Li is finishing work on a study of polar rays. She has found that the rays are connected with the coronal structure of active regions, and are seen over the pole in projection. Synoptic maps of coronal emission show both solar cycle and annual effects, from the latitudes of active regions and the nodding of the solar B0 angle. High temperature emissions show the polar rays best, because of the high pressure scale height of the hot material. This is being written up for submission to ApJ Letters. ============================================================ Stanford Univ Activity Report for Feruary and March 2000 ============================================================ (P. Sturrock) Peter has prepared an article on the CME problem, in collaboration with Mike Wheatland of Sydney and Rich Wolfson of Middlebury. They consider the energetic requirement for a twisted flux tube to erupt through an overlying magnetic arcade. The initial configuration comprises a twisted flux tube of finite length, held down by the arcade. The final state comprises an untwisted flux tube that has ruptured the arcade and expanded into interplanetary space. Comparison of the total energy of the initial and final configurations leads to an estimate of the twist required for an eruption to be energetically possible. It turns out that this condition is significantly less restrictive than the condition that the flux tube be unstable according to linear MHD theory. The implication is that such configurations can be metastable - i.e stable against small perturbations but unstable against sufficiently large perturbations. This is the requirement for explosive instability, such as is required to explain a sudden event such as a flare or a coronal mass ejection. Page 14 In another aspect of the CME research described in the previous paragraph, Peter continues to collaborate with Mike Wheatland (in Sydney) concerning the energy content of stressed magnetic fields. In particular, they are exploring the possibility that, if a field configuration contains a component that is detached from the photosphere, it may have more energy than the corresponding open configuration. We are therefor examining a configuration in which a closed magnetic toroid, located at the equator, is held in place by an overlying arcade-type magnetic field. Field lines of the overlying field are rooted in the photosphere, but field lines in the toroid are not. Peter and Mike are negotiating to determine a field configuration that meets the above requirements, but is susceptible to computer analysis. Peter continues to collaborate with Mike and with Jim McTiernan in Berkeley, concerning the optimization-function approach to the reconstruction of force-free magnetic field configurations from photospheric vector magnetograph data. The optimization-function method rests on the minimization of the integral of a sum of terms, each term being the square of the error in each relevant equation. One difficulty has been that it is necessary to specify (or guess) the magnetic field on the outer surfaces (away from the photosphere). We have found that we can generalize the optimization procedure by multiplying each term by a weighting function, and arranging that each such weighting function drops to zero at the outer surface of the domain. The boundary condition on that surface then becomes irrelevant, so that it is not necessary to specify the field on the outer surfaces. Jim has run a test case and funds that the calculation is convergent. Publications Roald, C.B., Sturrock, P.A., & Wolfson, R. 1999, The dependence of coronal heating on magnetic flux density in the photosphere, Ap J, in press. Sturrock, P.A., Wheatland, M.S., & Wolfson, R. 2000, Metastable magnetic configurations and their significance for coronal mass ejections. Ap J, to be submitted. Wolfson, R., Roald, C.P., Sturrock, P.A., and Weber, M. 1999, Coronal X-ray brightness and photospheric magnetic field: A study in correlations, ApJ, in press Wheatland, M.S., Sturrock, P.A., & Roumeliotis, G. 1999, An optimization approach to reconstructing force-free fields, ApJ, submitted. Page 15 =========================================================================== Solar Physics Research Corp. Activity Report for Feruary and March 2000 =========================================================================== (Karen L. Harvey and Hugh S. Hudson) KAREN L. HARVEY: Activities for February and March: (1) It has become apparent is the analysis of the NSO/KP He I 10830 rotation maps that a detailed comparison with coronal data is needed to ascertain if the structures identified as coronal holes in He I 10830 correspond to low coronal emission or are in fact some other coronal feature. This aspect of our analysis continued through the last two months, along with investigating the the formation process of coronal holes, that is, what new connections are established with the evolution of the magnetic fields of emerging and dispersing active regions that lead to the formation of isolated, sub-polar holes. Of note in this process may be the existence of linear zones that separate systems of X-ray loops that are directed in opposite directions, resembling a `hairpart'. (2) In a project with Terry Forbes, we are now in the process of identifying He I 10830 2-ribbon flares associated coronal holes and long-duration X-ray arcades change using the NSO/KP He I 10830 spectroheliograms. The period being surveyed extends from September 1991 to the present. A few well observed events will be selected on the basis that (1) there is good temporal coverage by the SXT full-frame images, (2) the position of the event is on the solar disk at a location to minimize the geometrical effects in the line-of-sight magnetic flux measurements, and (3) the boundaries of the transient coronal holes can be established using the SXT images and He I 10830 spectroheliograms. The objective of this study is to determine the reconnection rate as the open magnetic fields with the transient hole form into the closed loops of the arcade. (3) Updating of the Yohkoh/SXT publication list. (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. Planned Activities for April and May 2000: Continued analysis of (1) the spatial and temporal correspondence of coronal holes observed in He I 10830 spectroheliograms and the SXT full-frame images; (2) a study with T. Forbes of the reconnection rate of magnetic fields using long-duration arcade events/He I 10830 2-ribbon flares associated with X-ray dimming and transient coronal holes. Terry Page 16 Forbes will be visiting Tucson in early May to work on this effort. HUGH S. HUDSON Activities for February and March: I attended three meetings during these two months: the MR2000 meeting on magnetic reconnection in Tokyo; a CDAW on "solar eruptive events" at Catholic University in Maryland, and the ISTP workshop at GSFC. The various presentations for these meetings are all on Web pages at http://isass1.solar.isas.ac.jp/~hudson/talks. One of the highlights from this ambitious schedule of presentations was the fact that I recruited Ed Cliver to be a co-author on the paper "Non-coronagraphic observations of CMEs", presented at the Catholic U. meeting and (I hope) to appear in JGR. This is an extremely worthwhile review subject, and in the process of preparing for the presentation, I created the new "Grand Archive of Flare Cartoons", http://isass1.solar.isas.ac.jp/~hudson/cartoons, which seems to be popular. In the last of these presentations, because Tsuneta was unable to attend the meeting, I reviewed the Yohkoh evidence for large-scale magnetic reconnection processes in flares and CMEs. My conclusion is basically that we see many of the "correct" signatures, but that we still don't understand the reasons for what we observe. I now understand better why I believe that a cusp configuration does not directly imply ongoing reconnection, incidentally. Not much else other than SXT operations got done, except that I've been discussing the limitations of SXT temperature measurements with Nitta and Acton. It may be possible for us to take a step beyond the key work of Siarkowski et al. in understanding the effects of pointing jitter on these data. Planned Activities for April and May 2000: 1. Finish the May 6 wave paper, hoping to get it out the door before the 2nd anniversary of its SXT science nugget (December 25). 2. Finish the Cliver paper on non-coronagraphic observations. 3. Attend (late May) a workshop at ISSI (Bern) on unresolved structure. My interests here center on (a) nanoflares, and (b) the physics of the "supra-arcade downflows", i.e. what determines the spatial structure, both horizontal and vertical. PUBLICATIONS: Papers Published "Coronal Magnetic Implosions": H. S. Hudson, ApJ 531, L75 (2000). Page 17 "Coronal Magnetic Implosions": Yohkoh 8th anniversary symposium proceedings (extended abstract) Papers Accepted "Sigmoids as Precursors of Solar Eruptions": R. Canfield, H. Hudson, and A. Pevtsov, IEEE Transactions On Plasma Science, Special Issue on Space Plasmas, 2000. Papers Submitted "Detection of Coronal Dimming in Microwaves", N. Gopalswamy, Y. Hanaoka, and H. Hudson (ApJ, 2000) Page 18 ------------------------------------------------------------------------------- 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 March 2000 February 2000 |------------------------------- | 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 February 2000 |------------------------------- |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 | 18 | ------------------------|------------------------|-----------------|----------- For sale by: Superintendent of Documents, U.S. Government Printing Office