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MEETING OF INTERNATIONAL SOLAR CYCLE STUDIES: WORKING GROUP 2:
Solar Magnetic Field Variability Study: From the Lower Atmosphere through the Inner Corona

Coordinators: R. Harrison and TBD

Nagoya, Japan; July 11, 1998

The International Solar Cycle Studies (ISCS) program has been approved by the ICSU and SCOSTEP. ISCS is an international program of research with the goal of specifying the space environment during the rise and maximum of solar cycle 23: 1998-2002. We will be holding our first meeting just before COSPAR which is to be held in Nagoya, Japan; July 12-19, 1998. The ISCS meeting will be held at the Nagoya Congress Center, the same location as the COSPAR meeting. The ISCS meeting will an all-day meeting on Saturday, July 11, and will consist of invited and contributed papers with ample time for discussion.

The research program of ISCS is divided among three Working Groups. This is an invitation to join WG2 - Solar Magnetic Field Variability Study: From the Lower Atmosphere through the Inner Corona. The Coordinators of WG2 are R. Harrison ( Harrison@solar.stanford.edu) and (interium) S. T. Wu (wus@cspar.uah.edu). You are also invited to participate in our first meeting with ISCS in Nagoya.

It is recognized that solar atmospheric structures are dominated by magnetic fields. The variability of the solar magnetic field must be investigated to understand the physics of solar activity. For these studies we will classify the variability in different time and spatial scales. For example, we need to study the solar magnetic field variability on both a global spatial scale and on a long time scale to understand the changes during the rising and maximum portions of a solar cycle. We also must study the magnetic field variability on a short time scale (hours, days, or even months) in both small and global spatial scale. This would improve our knowledge of the fundamental physical processes for the evolution of active regions and corona magnetic fields leading to a better understanding of disturbances in the lower solar atmosphere (i.e. UV , EUV and X-Ray emissions) and in the corona (e.g. coronal mass ejections).

Another important aspect of near-Sun coronal phenomena is the prolonged post-CME (Coronal Mass Ejection) energy release in the corona. During this phase, the magnetic field in the extended region of the corona, strong disturbed by a large CME, relaxes via the magnetic reconnection in vertical coronal current sheets. The post-eruption energy release is a process which appears to occur in any eruptive event, including a CME, irrespective of whether a CME is associated by impulsive flare energy release, by filament (i.e. prominence)eruption, or by the destabilization of a large-scale coronal structure. An investigation of the magnetic structure of solar active regions both pre- and post-coronal mass ejections may offer insight as to if and when a region will produce a similar eruption.

The objective of this working group is to investigate solar magnetic field variabilities for small and global spatial structures and for both long and short time scales. In the initial phase of this project, we will focus on the short time scale solar features with small and global spatial structures. To conduct these studies, we will utilize data collected by experiments on-board various space missions (SOHO, YOHKOH, TRACE, ULYSSES, WIND, and GOES) in addition to data from and ground-based measurements.

Specific task are cited below.

1. Coronal loop structures and evolution: The coronal loops are fundamental elements of the solar atmosphere. In order to understand the physics (i.e. UV, EUV, X-Ray emissions) of the non-coronal hole corona, it is essential to investigate the structures and evolution of coronal loops. These loops are formed by the plasmas confined by the solar magnetic fields. These studies are particularly important for the understanding of flrae physics.
2. Initiation and propagation of coronal mass ejections (CMEs) and their interplanetary consequences: It has been suggested that most CMEs are caused by the destabilization of the coronal streamers on the basis of previous observations. The current space instrument LASCO/EIT on-board the SOHO mission has a field-of-view of the Sun in the range from 1 solar radii to 32 solar radii which, in collaboration with coronal spectrometers also on SOHO, provides an unprecedented opportunity to investigate the initiation and propagation of CMEs and their interplanetary consequences. Therefore, we suggest utilization of these observations to answer the following questions: (i) What physical processes lead to global scale coronal magnetic field? This could lead to an understanding of the initiation of CMEs. (ii) What is a coronal mass ejection? (iii) What is the rate? How does it relate to the solar cycle?
3. Frequency of the occurrence of the CMEs during the rising phase of the solar cycle 23: The CME is a major restructuring of the corona. It is important to assess the role of CMEs in the solar cycle. SOHO is ideally suited to this work.
4. Theoretical Modeling and Numerical Simulations: In order to carry out the above objectives, we will also focus our attention to the development of theoretical and numerical simulation models to quantify the interpretation of the observation in order to reveal the hidden physics. It is also to emphasize that this group will work closely with both WG1 and WG3 by taking the solar surface input from WG1 and delivering the outputs of WG2 to WG3.

For more information on the ISCS program see the Web page at: http://cspar.uah.edu/iscs/

If you are interested in participating in the activities of Working Group 2, whether or not you can attend the ISCS meeting in Japan, please send the following pertinent information to both S. T. Wu and R. Harrison. Send us this information as soon as you can, but before April 30, and preferably by E-mail to: wus@cspar.uah.edu or Harrison@solar.stanford.edu

Our post addresses are:

S. T. Wu					Richard A. Harrison 
CSPAR						Astrophysics Division
The University of Alabama in Huntsville		Rutherford Appleton Laboratory
Huntsville, AL  35899 USA			Chilton, Didcot
1 (256) 890-6413				Oxfordshire OX11 0QX
1 (256) 890-6382 Fax				UNITED KINGDOM

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