The solar cycle variation of coronal mass ejections and the solar wind mass flux

TLDR

Coronal mass ejections are a key coronal phenomenon that can perturb the solar wind mass flux, and recent data now allow long‑term occurrence studies. The study examines CME occurrence rates over an entire 11‑year solar cycle and compares them with other CME‑related activity and the 1‑AU solar wind particle flux. The analysis corrects CME rates for instrument duty cycles, visibility functions, mass detection thresholds, and geometrical effects. CME frequency tracks the solar cycle in amplitude and phase, corrected rates from different instruments agree, no single activity metric outperforms others in correlation, the CME‑to‑solar‑wind mass flux ratio follows the cycle, and CMEs contribute about 15 % of the near‑ecliptic solar wind mass flux at solar maximum.

Abstract

Coronal mass ejections (CMEs) are an important aspect of coronal physics and a potentially significant contributor to perturbations of the solar wind, such as its mass flux. Sufficient data on CMEs are now available to permit study of their longer‐term occurrence patterns. Here we present the results of a study of CME occurrence rates over more than a complete 11‐year solar sunspot cycle and a comparison of these rates with those of other activity related to CMEs and with the solar wind particle flux at 1 AU. The study includes an evaluation of corrections to the CME rates, which include instrument duty cycles, visibility functions, mass detection thresholds, and geometrical considerations. The main results are as follows: (1) The frequency of occurrence of CMEs tends to track the solar activity cycle in both amplitude and phase; (2) the CME rates from different instruments, when corrected for both duty cycles and visibility functions, are reasonably consistent; (3) considering only longer‐term averages, no one class of solar activity is better correlated with CME rate than any other; (4) the ratio of the annualized CME to solar wind mass flux tends to track the solar cycle; and (5) near solar maximum, CMEs can provide a significant fraction (i.e., ≈ 15%) of the average mass flux to the near‐ecliptic solar wind.