Solar wind from high-latitude coronal holes at solar maximum

Abstract

In this study we combine Ulysses' observations from the solar wind plasma (SWOOPS) and ion composition (SWICS) instruments to study high-latitude coronal holes near solar maximum for the first time. While chromospheric and coronal composition signatures indicate that there is a unique type of solar wind, which flows from coronal holes, variations in the acceleration process produce a wide range of solar wind speeds from these holes. High-speed wind (>700 km s^-1) can be produced in small as well as large holes, although the very highest speed non-transient winds do come from the centers of the largest holes. Along the edges of coronal holes, the acceleration decreases and freezing-in temperatures increase relatively smoothly into the surrounding solar wind, indicating a transition layer around the edges of coronal holes.