Solar cycle changes in coronal holes and space weather cycles

Abstract

Potential field source surface models of the coronal magnetic field, based on Mt. Wilson Observatory synoptic magnetograms, are used to infer the coronal hole sources of low‐heliolatitude solar wind over approximately the last three solar cycles. Related key parameters like interplanetary magnetic field and bulk velocity are also calculated. The results illustrate how the evolving contribution of the polar hole sources relative to that from low‐latitude and midlatitude active region hole sources can explain solar magnetic field control of long‐term interplanetary variations. In particular, the enduring consistent magnetogram record and continuous model displays produce a useful overview of the solar control of interplanetary cycles and trends that affect space weather.