The differences in the origination and properties of the near-Earth solar wind between solar cycles 23 and 24

TL;DR

This study compares the sources and properties of near-Earth solar wind between solar cycles 23 and 24, revealing cycle-dependent variations in composition, speed, and origin regions using an improved back-mapping method.

Contribution

It introduces an enhanced two-step mapping procedure that accounts for initial acceleration, enabling more accurate tracing of solar wind sources across two solar cycles.

Findings

Higher CH and AR wind proportions in SC 23 compared to SC 24.

Solar wind parameters like speed and helium abundance are generally higher in SC 23 during maximum and declining phases.

Significant decrease in charge states during SC 23's solar minimum.

Abstract

The dependence of the sources and properties of the near-Earth solar wind on solar cycle activity is an important issue in solar and space physics. We use the improved two-step mapping procedure that takes into account the initial acceleration processes to trace the near-Earth solar winds back to their source regions from 1999 to 2020, covering solar cycles (SCs) 23 and 24. Then the solar wind is categorized into coronal hole (CH), active region (AR), and quiet Sun (QS) solar wind based on the source region types. We find that the proportions of CH and AR (QS) wind during SC 23 are higher (lower) than those during SC 24. During solar maximum and declining phases, the magnetic field strength, speed, helium abundance (AHe), and charge states of all three types of solar wind during SC 23 are generally higher than those during SC 24. During solar minimum, these parameters of solar wind are generally lower during SC 23 than those during SC 24. There is a significant decrease in the charge states of all three types of solar wind during the solar minimum of SC 23. The present statistical results demonstrate that the sources and properties of the solar wind are both influenced by solar cycle amplitude. The temperatures of AR, QS, and CH regions exhibit significant difference at low altitudes, whereas they are almost uniform at high altitudes.