Characterizing the Alfvénic slow wind: A case study

Alfvenicity is a feature characterizing solar wind fluctuations and is defined by a high correlation between velocity and magnetic field components and in ideal conditions by equipartition between kinetic and magnetic energies. It is a feature characterizing especially the fast wind while slow wind shows usually lower correlation between velocity and magnetic field components. However this is not always the case. Under certain conditions a high degree of Alfvenicity can be found also within slow wind. In the present paper, we show the existence of two kinds of slow solar wind with similar velocities but which display different characteristics. The different degree of Alfvenicity is a feature discrimanating the two types of slow wind. This feature is always linked to a low magnetic field compressibility as shown in the present paper using a case study. It is found that the Alfvenic slow wind is more similar to fast wind rather than to the standard slow wind apart from velocity. This fact can be attributed ...