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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
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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"
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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.
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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.
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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.
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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.
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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
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=======================================================================
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
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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/
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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.
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=============================================================
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 |
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