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See detailSECCHI observations of the Sun-s Garden-Hose Density spiral
Sheeley, N.R.; Herbst, A.D.; Palatchi, C.A. et al

in The Astrophysical Journal (2008), 674

The SECCHI HI2 white-light imagers on the STEREO A and B spacecraft show systematically different proper motions of material moving outward from the Sun in front of high-speed solar wind streams from ... [more ▼]

The SECCHI HI2 white-light imagers on the STEREO A and B spacecraft show systematically different proper motions of material moving outward from the Sun in front of high-speed solar wind streams from coronal holes. As a group of ejections enters the eastern (A) field of view, the elements at the rear of the group appear to overrun the elements at the front. (This is a projection effect and does not mean that the different elements actually merge.) The opposite is true in the western (B) field; the elements at the front of the group appear to run away from the elements at the rear. Elongation/time maps show this effect as a characteristic grouping of the tracks of motion into convergent patterns in the east and divergent patterns in the west, consistent with ejections from a single longitude on the rotating Sun. Evidently, we are observing segments of the “garden-hose” spiral made visible when fast wind from a low-latitude coronal hole compresses blobs of streamer material being shed at the leading edge of the hole. [less ▲]

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See detailHeliospheric Images of the Solar Wind at Earth
Sheeley,, N.R.; Herbst, A.D.; Palatchi, C.A. et al

in The Astrophysical Journal (2008), 675

During relatively quiet solar conditions throughout the spring and summer of 2007, the SECCHI HI2 white-light telescope on the STEREO B solar-orbiting spacecraft observed a succession of wave fronts ... [more ▼]

During relatively quiet solar conditions throughout the spring and summer of 2007, the SECCHI HI2 white-light telescope on the STEREO B solar-orbiting spacecraft observed a succession of wave fronts sweeping past Earth.We have compared these heliospheric images with in situ plasma and magnetic field measurements obtained by near-Earth spacecraft, and we have found a near perfect association between the occurrence of these waves and the arrival of density enhancements at the leading edges of high-speed solar wind streams. Virtually all of the strong corotating interaction regions are accompanied by large-scale waves, and the low-density regions between them lack such waves. Because the Sun was dominated by long-lived coronal holes and recurrent solar wind streams during this interval, there is little doubt that we have been observing the compression regions that are formed at low latitude as solar rotation causes the high-speed wind from coronal holes to run into lower speed wind ahead of it. [less ▲]

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