34th Solar Physics Division Meeting, June 2003
Session 4 Corona II
Poster, Monday, June 16, 2003, 3:30-5:00pm, Mezzanine

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[4.11] Observation of Two Forms of Macrospicules in Coronal Holes: Spikes and Loops

Y. Yamauchi (NASA/MSFC/NRC), R.L. Moore, S.T. Suess (NASA/MSFC), H. Wang (NJIT/BBSO), T. Sakurai (NAOJ)

Ulysses high-latitude observations show the existence of small structures in the high-speed solar wind that contain magnetic field reversals. These reversals sometimes appear to be associated with plasmoids or current sheets. We have proposed that the reversals are created by activity low in the magnetic network in coronal holes [Yamauchi et al., 2002, GRL, v29(10)]. Here we present solar evidence favoring this hypothesis. Since photospheric magnetic flux observations have shown that there is a small fraction of opposite polarity in coronal holes [e.g., Deforest et al., 1997, Sol. Phys., v175(2), 393-410], there should be local magnetic loops in the network. If one of these loops were to erupt into the corona, it could create a magnetic field reversal by reconnection with the surrounding open magnetic field. Tanaka [1972, Report of BBSO, No. 125] observed that some H-alpha mottles (spicules) in the network show a double-strand structure. The two strands might be the legs of an erupted network loop. Any coronal hole macrospicule that showed a bipolar erupting loop structure rather than a unipolar, jet-like spike, would be a candidate for such an event. From sequences of full-disk H-alpha images from Big Bear Solar Observatory, we have found 35 macrospicules in polar coronal holes. About half of these appear to be erupting loops, while the rest look more like unipolar spikes. Thus, we have found evidence that network-scale erupting magnetic loops are a common occurrence in coronal holes. This strengthens the possibility that such events are the source of the fine-scale field reversals in the high-speed wind.

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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.