On the relation between coronal hole latitude range and the speed of the solar wind at Earth’s bowshock

Abstract

This study is based on latitude measurements at the helio-meridian of two trans-equatorial coronal holes. After applying a simple algorithm based on super-radial expansion to the observation times, and translating these times to Earth’s bowshock, the measurements are compared with those of solar wind speed observed by the Wind and ACE spacecraft at those times. These comparisons reveal a causal relationship between the latitude range of the coronal hole open flux and the solar wind speed at the bowshock. Regression formulae are provided for predicting the speed of the fast solar wind from the latitude range of the coronal hole boundary within20±of the helioequator.