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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 24, issue 2
Ann. Geophys., 24, 785–789, 2006
https://doi.org/10.5194/angeo-24-785-2006
© Author(s) 2006. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 24, 785–789, 2006
https://doi.org/10.5194/angeo-24-785-2006
© Author(s) 2006. This work is distributed under
the Creative Commons Attribution 3.0 License.

  23 Mar 2006

23 Mar 2006

Alfvénic turbulence in solar wind originating near coronal hole boundaries: heavy-ion effects?

B. Bavassano1, N. A. Schwadron2, E. Pietropaolo3, and R. Bruno1 B. Bavassano et al.
  • 1Istituto di Fisica dello Spazio Interplanetario, Istituto Nazionale di Astrofisica, Rome, Italy
  • 2Department of Astronomy, Boston University, Boston, Massachusetts, USA
  • 3Dipartimento di Fisica, Università di L’Aquila, L’Aquila, Italy

Abstract. The mid-latitude phases of the Ulysses mission offer an excellent opportunity to investigate the solar wind originating near the coronal hole boundaries. Here we report on Alfvénic turbulence features, revealing a relevant presence of in-situ generated fluctuations, observed during the wind rarefaction phase that charaterizes the transition from fast to slow wind. Heavy-ion composition and magnetic field measurements indicate a strict time correspondence of the locally generated fluctuations with 1) the crossing of the interface between fast and slow wind and 2) the presence of strongly underwound magnetic field lines (with respect to the Parker spiral). Recent studies suggest that such underwound magnetic configurations correspond to fast wind magnetic lines that, due to footpoint motions at the Sun, have their inner leg transferred to slow wind and are stretched out by the velocity gradient. If this is a valid scenario, the existence of a magnetic connection across the fast-slow wind interface is a condition that, given the different state of the two kinds of wind, may favour the development of processes acting as local sources of turbulence. We suggest that heavy-ion effects could be responsible of the observed turbulence features.

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