| Budget Amount *help |
¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1996: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1995: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
Planar magnetic structures in which interplanetary magnetic field vector takes almost all directions that are parallel to a plane are correlated with EXPANDING ACTIVE REGIONS on the Sun by using Sakigake solar wind data and Yohkoh soft X-ray images of the Sun. During the period from January to July, 1993, we could identify three typical planar magnetic structures with the active region expansions found by Uchida et al. [1992] in the Yohkoh soft X-ray images, from which loop-like structures of active-region corona expand outward repeatedly at speeds of a few to a few tens of km/s even in the absence of any sizable flares. The active region expansions are expected to play an important role in mass loss from the Sun. On the other hand, not all the active regions were observed as planar structures in interplanetary space. In 16 Sakigake observations of solar wind plasma whose solar sources coincided with active regions, 9 had non-spiral magnetic field including planar structures, high ion density or both of them, but the other 7 (44%) exhibited no significant difference from average solar wind with spiral field.
Pressure gradient in the solar wind is examined as a candidate cause of planar magnetic structures. In five of Sakigake planar magnetic structures with no bulk-speed gradient, two were in the regions of pressure gradient but the others were not. Flattened, intertwined flux tubes of high-beta plasma (Crooker et al., 1996) are re-examined to model planar magnetic structures. In order to reproduce a planar magnetic structure, a large number of flux ropes with small helicity are required. Variation of field direction is mainly due to variation of orientation of rope axs, rather than to field rotations in each of ropes.
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