SH53A-2474
STEREO Observations of Small Transients in the Solar Wind at 1 AU (2007-2014) and Comparison with Near – Earth Results from Wind (1995 - 2014)
Friday, 18 December 2015
Poster Hall (Moscone South)
Wenyuan Yu1, Charles J Farrugia1, Antoinette Broe Galvin2, Noé Lugaz1, Janet G Luhmann3 and Kristin Simunac4, (1)University of New Hampshire Main Campus, Durham, NH, United States, (2)Univ of New Hampshire, Durham, NH, United States, (3)University of California Berkeley, Berkeley, CA, United States, (4)Organization Not Listed, Washington, DC, United States
Abstract:
The occurrence frequency of small transients (STs) in the solar wind increases dramatically during solar activity minimum. With observations from the Wind spacecraft we could observe STs near Earth over a period of 20 years. Now we also have measurements by the STEREO spacecraft, which observe at 1 AU as they separate from Earth by 22.5 degrees per year. Hence we have an unprecedented opportunity to study the STs at the far side of the Sun at 1 AU, and examine their distribution over solar cycle activity (~ 8 years). We show their properties per year at STEREO, and compare them with Wind’s results. The occurrence of STs is found to be anti-correlated with that of ICMEs (STs are frequently observed in the solar minimum while the ICMEs are fewer). We then model some flux-rope type STs by non-force free models, both analytical and numerical ones. Most of the fitting results show that the cross-section of the small flux ropes tends to be elliptical. Finally we show how their orientations are distributed at 1 AU.
