Dependence of solar wind speed on the local magnetic field orientation: Role of Alfvénic fluctuations
Article first published online: 28 JAN 2014
©2013. The Authors.
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
Geophysical Research Letters
Volume 41, Issue 2, pages 259–265, 28 January 2014
How to Cite
2014), Dependence of solar wind speed on the local magnetic field orientation: Role of Alfvénic fluctuations, Geophys. Res. Lett., 41, 259–265, doi:10.1002/2013GL058482., , , and , (
- Issue published online: 3 MAR 2014
- Article first published online: 28 JAN 2014
- Accepted manuscript online: 26 DEC 2013 07:56PM EST
- Manuscript Accepted: 18 DEC 2013
- Manuscript Revised: 16 DEC 2013
- Manuscript Received: 29 OCT 2013
- Solar wind;
- Alfvénic fluctuations;
- interplanetary magnetic field
We report an analysis of correlations between magnetic field and velocity fluctuations in the fast solar wind beyond 1 AU at high latitudes. We have found that on scales shorter than the microstream structures, there exists a well-defined dependence of the flow speed on the angle between the magnetic field vector and the radial direction. Solar wind is found to be slightly faster when the measured magnetic field vector is transverse to the velocity, while it is always slower when the magnetic field is parallel, or antiparallel, to the radial direction. We show that this correlation is a direct consequence of the high Alfvénicity of fast wind fluctuations and that it can be reasonably described by a simple model taking into account the main properties of the low-frequency antisunward Alfvén fluctuations as observed in the solar wind plasma. We also discuss how switchbacks, short periods of magnetic field reversals, naturally fit in this new observed correlation.