# On slow solar wind with high Alfv\'enicity: from composition and microphysics to spectral properties

## TL;DR

This paper investigates the properties and origins of Alfvénic slow solar wind, revealing similarities with fast wind and discussing implications for solar missions and turbulence studies.

## Contribution

It presents a comprehensive analysis of Alfvénic slow solar wind, linking its microphysics, spectral features, and source regions, highlighting its similarities to fast wind from coronal holes.

## Key findings

- Alfvénic slow wind shares characteristics with fast wind, likely from coronal-hole origins.
- Super-radial expansion influences the lower velocity of Alfvénic slow wind.
- Implications for turbulence measurements near the Sun are discussed.

## Abstract

Alfv\'enic fluctuations are very common features in the solar wind and are found especially within the main portion of fast wind streams while the slow wind usually is less Alfv\'enic and more variable. In general, fast and slow wind show many differences which span from the large scale structure to small scale phenomena including also a different turbulent behaviour. Recent studies, however, have shown that even slow wind can be sometimes highly Alfv\'enic with fluctuations as large as those of the fast wind. The present study is devoted to present many facets of this Alfv\'enic slow solar wind including for example the study of the source regions and their connection to coronal structures, large-scale properties and micro-scale phenomena and also impact on the spectral features. This study will be conducted performing a comparative analysis with the typical slow wind and with the fast wind. It has been found that the fast wind and the Alfv\'enic slow wind share common characteristics, probably attributable to their similar solar origin, i.e. coronal-hole solar wind. Given these similarities, it is suggested that in the Alfv\'enic slow wind a major role is played by the super-radial expansion responsible for the lower velocity. Relevant implications of these new findings for the upcoming Solar Orbiter and Solar Probe Plus missions, and more in general for turbulence measurements close to the Sun, will be discussed.