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Ann. Geophys., 21, 1257-1261, 2003
www.ann-geophys.net/21/1257/2003/
© European Geosciences Union 2003
How did the solar wind structure change around the solar maximum? From interplanetary scintillation observation
K. Fujiki1, M. Kojima1, M. Tokumaru1, T. Ohmi1, A. Yokobe1,*, K. Hayashi1, D. J. McComas2, and H. A. Elliott2
1Solar-Terrestrial Environment Laboratory, Nagoya University, 3-13 Honohara, Toyokawa, Aichi, Japan
2Southwest Research Institute, San Antonio, TX, USA
*SGI Japan, Ltd., 4-20-3 Ebisu, Shinjuku, Tokyo, Japan
Abstract. Observations from the
second Ulysses fast latitude scan show that the global structure of solar wind
near solar maximum is much more complex than at solar minimum. Soon after solar
maximum, Ulysses observed a polar coronal hole (high speed) plasma with
magnetic polarity of the new solar cycle in the Northern Hemisphere. We analyze
the solar wind structure at and near solar maximum using interplanetary
scintillation (IPS) measurements. To do this, we have developed a new
tomographic technique, which improves our ability to examine the complex
structure of the solar wind at solar maximum. Our IPS results show that in 1999
and 2000 the total area with speed greater than 700 km s-1 is
significantly reduced first in the Northern Hemisphere and then in the Southern
Hemisphere. For year 2001, we find that the formation of large areas of fast
solar wind around the north pole precedes the formation of large polar coronal
holes around the southern pole by several months. The IPS observations show a
high level agreement to the Ulysses observation, particularly in coronal holes.
Key words. Interplanetary physics
(solar wind plasma) – Radio science (remote sensing)
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