Multi-wavelength Observations of Coronal Structure and Dynamics, Yohkoh 10 Anniversary Meeting

461 Pages·2002·11.83 MB·English

by  Petrus C.H. Martens and David P. Cauffman (Eds.)

COSPAR COLLOQUIA SERIES
VOLUME 13
MULTI-WAVELENGTH OBSERVATIONS OF
CORONAL STRUCTURE AND DYNAMICS
Yohkoh Anniversary Meeting
10 th
PERGAMON
Yohkoh Spacecraft Illustration:
The Yohkoh spacecraft was named through a contest among Japanese schoolchildren. The name
means "Sunbeam"
Cover Illustration:
This full disk 1991 Yohkoh-SXT image was selected by the readers of Sky an Telescope magazine
as one of the 10 most inspiring astronomical images of the 20 th century (January 2000 issue. Photo
credit: Greg Slater).
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MIALTI-WAVELENGTH OBSERVATIONS
OF
CORONAL STRUCTURE AND DYNAMICS
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Yohkoh 10 th Anniversary Meeting
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Proceedings of the COSPAR Colloquium
Held in Kona, Hawaii, USA
20-24 January, 2002 "
Edited by
Petrus C. H. Martens
Department of Physics, Montana State University
P. O.Box 3840
Bozeman, MT 59717 USA
and
David P. Cauffman
Lockheed Martin Advanced Technology Center
3251 Hanover Street, Palo Alto CA 94304 USA
now at:
8111 Possession Ridge Lane, Clinton WA 98236 USA
2002
PERGAMON
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PREFACE
These are the Proceedings of the Yohkoh 10 th Anniversary Meeting, a COSPAR Colloquium held in Kona,
Hawaii, USA, on January 20-24, 2002. There were 133 participants from 14 countries. The Colloquium was
sponsored by (in no specific order) COSPAR, NASA, the MSU Solar Physics Group, LMSAL, ISAS, the
Solar Physics Research Corporation, Elsevier Science, and the NSF. Thanks to the largesse of these sponsors
the conference organizers were able to provide financial assistance in part or in whole to 30 participants.
The meeting had originally been planned for September 2001 at the same location, but had to be postponed
due to the difficulty in travel following the terrible events of September 11, 2001. We appreciate the
understanding and flexibility of the participants and of the conference hotel in rescheduling this meeting.
The title of the meeting was Multi-Wavelength Observations of Coronal Structure and Dynamics. We
reviewed the many and varied advances in our understanding of the dynamic solar atmosphere in the
past ten years of observations by Yohkoh, often in collaboration with SOHO, TRACE, Ulysses, and many
ground-based observatories. The Scientific Organizing Committee made a concerted effort to invite younger
scientists to present the Invited Reviews. This was a success and we have a large number of excellent review
papers in this volume. This policy had the additional positive effect of freeing up several of the senior
scientists to present exciting new results from their own research in contributed talks. The large number of
different sessions in these Proceedings reflects the large variety in science topics that are being addressed
with Yohkoh data. In all, these Proceedings reflect the quality, breadth, and depth of solar physics research
inspired by the decade of Yohkoh observations.
The introductory talk for the meeting was given by Prof. Atsuhiro Nishida, former Director-General of ISAS,
the lead institute for the Yohkoh mission. After that Prof. Takeo Kosugi (see the next paper) of ISAS gave
us a succinct and very clear description of the events that had led to the unfortunate Yohkoh accident on
December 14, 2001, and of the recovery efforts that were underway at the time of the meeting. Prof. Kosugi
also chaired the final session in which Prof. Ogawara (also ISAS), the Yohkoh Project Manager, received a
well deserved ovation for his unfailing efforts in leading the Yohkoh project from its conception to end, and
the Yohkoh instrument builders were recognized.
The meeting was held at the lovely King Kamehamea Beach Hotel in Kona on the Big Island of Hawaii.
This wonderful setting, and the friendly and helpful hotel staff made for a relaxed yet focused atmosphere.
Social events included a welcome reception, a traditional Hawaiian Luau with a performance of dances from
several of the Pacific island groups, and tours of the Keck and Subaru Observatories at Mauna Kea or the
HAO Coronagraph Station at Mauna Loa. It is perhaps fitting that this milestone Yohkoh Anniversary
meeting was held in the Hawaiian Isles, because one of the first Yohkoh international meetings was also held
there, at the University of Hawaii in Oahu.
We are most grateful to the local organizing committee, in particular the professional work of Jana Halvorson,
and the great efforts of MSU graduate students Rebecca McMullen and Elizabeth Noonan. The LOC was
chaired by Profs. Loren Acton and Piet Martens of MSU. The computer setup worked flawlessly thanks
to the efforts of Alisdair Davey. We are also most grateful for the efforts of the members of the Scientific
Organizing Committee, chaired by the same persons as the LOC.
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Preface
We owe a special word of thanks to Dr. Mark Weber, who designed the LaTex template for the Proceedings
papers, and who has provided us continuous assistance with word processing problems, as well as with the
final edits of the papers.
The Yohkoh 10 th Anniversary Meeting was followed by a two day preparatory meeting at the same location
for the next major Japanese solar physics mission, Solar-B. This mission builds upon the success of Yohkoh
and promises to carry our understanding of the solar corona and photosphere even further. Again the US
and UK are international partners in some of the instruments. With several solar missions being prepared
by both NASA and ISAS for the current decade, and a growing recognition of the importance of space
weather, the future of solar physics seems bright.
The Editors:
Piet Martens
Dave Cauffman
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TEN YEARS OF YOHKOH AND ITS CURRENT STATUS:
A BRIEF SUMMARY
T. Kosugi 1 and L. W. Acton 2
1Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan
2physics Department, Montana State University, P.O. Box 1738~0, Bozeman, MT 59717, USA
ABSTRACT
The Yohkoh satellite was launched on August 30, 1991 by the Institute of Space and Astronautical Sci-
ence (ISAS) from its Kagoshima Space Center, and operated until December 14, 2001, despite having a
design goal of a lifetime of three years. Two of the onboard instruments were joint efforts with international
partners, namely the United States and the United Kingdom. In the ten years of operations since, Yohkoh
has acquired more than 6 million soft X-ray snapshot images and detected more than 2800 high energy
X-ray solar flares. More than a thousand papers by authors worldwide have been published from Yohkoh in
journals and proceedings, and a new generation of solar physicists has begun thesis research using Yohkoh
data.
DISCUSSION
The Yohkoh satellite was launched on August 30, 1991 by the Institute of Space and Astronautical Science
(ISAS) from its Kagoshima Space Center. It is a medium-sized satellite, 1 x 1 x 2 m in size and 400 kg in
weight, and carries four advanced X-ray (and gamma-ray) instruments for studying the solar corona and the
high-energy phenomena that take place there. They are the Soft X-ray Telescope (SXT), the Hard X-ray
Telescope (HXT), the Bragg Crystal Spectrometer (BCS), and the Wide-Band Spectrometer (WBS). The
SXT and the BCS were joint efforts with international partners, namely the United States and the United
Kingdom (USA-Japan for SXT and UK-USA-Japan for BCS). Science operations and data analysis have
been conducted by the same international framework. Yohkoh data have been made available to and been
utilized by the worldwide solar physics and related science communities, however. In addition, they have
been used by real-time, space-weather prediction services.
It was only after launch that we fully recognized the epoch-making excellence of the Yohkoh instruments,
which all worked just as designed. The dynamically changing nature of the solar corona was for the first time
vividly unveiled with high-quality, high-resolution, CCD images taken by SXT at high cadence. Acceleration
(and transport) of energetic electrons in solar flares became traceable with HXT, thanks to its imaging
capability in the purely nonthermal X-ray emission above 30 keV. In the subsequent years since then, we
have accumulated more than 6 million SXT snapshot images and detected with HXT more than 2800 solar
flares, together with their spectra from BCS and WBS.
More than a thousand papers have been published from Yohkoh in journals and proceedings. By the 10th
Anniversary of Yohkoh (August 30, 2001), 53 graduate students around the world had completed their
Yohkoh-related thesis work and received PhD doctorates. In Japan alone recipients of master of science
degrees have totaled 47. These papers and theses cover a wide variety of topics.
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Ten Years of Yohkoh and its Current Status: A Brief Summary
The following Yohkoh observations have revolutionized our view of the solar corona:
- Dynamically changing coronal structure involving magnetic reconnection with various temporal and spatial
scales, from microflares and jets to large-scale coronal restructuring events;
- Cusp-shaped soft X-ray arcades in long-duration event flares and above-the-loop-top hard X-ray sources
in impulsive flares as evidence for on-going magnetic reconnection in solar flares;
- Arcade formation and coronal dimming identified as the soft X-ray counterpart of coronal mass ejections
(CMEs), that are used for issuing alerts concerning the arrival of interplanetary disturbances at the Earth;
and
- Sigmoidal soft X-ray structures in active regions, identified as signatures of the likely onset of CMEs.
The cooperative nature of Yohkoh flight operations and data sharing fostered the creation of a unique file
structure and systems for data archive and analysis software. The Yohkoh data system has served as a model
for subsequent missions. The system of analysis software has evolved into the widely used SolarSoft or SSW
system that is increasingly becoming a standard for analysis of all kinds of solar observational data.
In addition to the science achievements mentioned above, we can be proud of Yohkoh for its successful public
outreach programs. Many science museums in the world exhibit Yohkoh SXT movies, which contribute to
making one of the modern science frontiers intimately available to the public. Similarly, internet outreach
programs have been developed and are frequently visited by interested audiences.
When we designed the Yohkoh satellite, three years of mission lifetime was a target. In this sense it is far
beyond our expectation that Yohkoh and its scientific instruments were perfectly operable for more than
a decade until December 14, 2001, when an unlucky accident was triggered the by transit of Yohkoh in
a solar near-total eclipse zone. Yohkoh's encounter with the eclipse caused an attitude control anomaly,
related to a defect in the software that had been installed when the control logic had been modified for
overcoming deterioration of one of the attitude actuators on board, and made the satellite lose its attitude
toward the Sun. As a consequence Yohkoh eventually lost its battery charge. None of the recovery efforts
were successful. Nonetheless, we believe that Yohkoh science will continue to develop. Yohkoh data is full
of many treasures to be analyzed, still hidden and still untouched.
REFERENCES
The Yohkoh instrument papers have been published in a special issue of Solar Physics, 136 (1991).
Initial results from Yohkoh have been published in a special issue of Publications of the Astronomical Society
of Japan, 44(5) (1992).
A comprehensive list of Yohkoh papers is posted at http://solar.physics.montana.edu/sxt/.
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Sponsored by
THE COMMITTEE ON SPACE RESEARCH (COSPAR)
THE NATIONAL AERONAUTICS AND SPACE ADMINISTRATION (NASA)
THE NATIONAL SCIENCE FOUNDATION (NSF)
THE INSTITUTE FOR SPACE AND ASTRONAUTICAL SCIENCE (ISAS)
THE MONTANA STATE UNIVERSITY SOLAR PHYSICS GROUP
LOCKHEED SOLAR AND ASTROPHYSICS LABORATORY
SOLAR PHYSICS RESEARCH CORPORATION
and
ELSEVIER SCIENCE
Scientific Organizing Committee
Co-Chairpersons"
Loren Acton (Montana State University)
Piet Martens (Montana State University)
Other Members:
David Alexander (Lockheed Martin Solar and Astrophysics Lab)
Len Culhane (Mullard Space Science Laboratory)
Leon Golub (Center for Astrophysics)
Richard Harrison (Rutherford Appleton Laboratory )
Takeo Kosugi (Institute of Space and Astronautical Science)
Barry LaBonte (Institute for Astronomy)
Yoshi Ogawara (Institute of Space and Astronautical Science)
Toshifumi Shimizu (National Astronomical Observatory of Japan)
Keith Strong (Lockheed Martin Solar and Astrophysics Lab)
Yutaka Uchida (Science University of Tokyo)
Organizing Committee
Loren Acton (Montana State University)
Piet Martens (Montana State University)
Jana Halvorson (free-lance creative services)
Elizabeth Noonan (Montana State University)
Rebecca McMullen (Montana State University)
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