The Influence of Magnetic Complexity of Active Regions on Solar Wind Properties During Solar Cycles 23 and 24

TL;DR

This work demonstrates that AR magnetic complexity, as classified by MWMC into α, β, and complex types, modulates the properties of the solar wind sourced from ARs during solar cycles 23 and 24. By linking Wind and ACE/SWICS data with 12-hour back-mapping of AR footpoints, the study shows that solar wind from complex ARs has stronger magnetic fields, higher $O^{7+}/O^{6+}$ and $Q_{Fe}$, and enhanced $A_{He}$ and FIP bias, while complex AR wind contributes disproportionately to AR wind relative to its AR prevalence. The results reveal that complex ARs are more effective at generating AR wind, likely due to more frequent magnetic reconnection and heating, which transport helium-rich material into the corona. The analysis also highlights how solar-cycle amplitude and instrumental factors (SWICS anomaly) influence measured distributions, underscoring the importance of handling pre- and post-anomaly data separately. Overall, the magnetic topology of ARs decisively shapes solar-wind heating, composition, and dynamics with implications for understanding solar wind generation mechanisms.

Abstract

Linking solar wind properties to the activities and characteristics of its source regions can enhance our understanding of its origin and generation mechanisms. Using the Mount Wilson magnetic classification (MWMC), we categorize all active regions (ARs) between 1999 and 2020 into three groups: alpha, beta, and complex ARs. Subsequently, we classify the near-Earth AR solar wind into the corresponding three types based on the magnetic type of ARs. Our results show that alpha, beta, and complex ARs account for 19.99%, 66.67%, and 13.34% of all ARs, respectively, while their corresponding AR solar wind proportions are 16.96%, 45.18%, and 37.86%. The properties of solar wind from different types of ARs vary significantly. As the magnetic complexity of ARs increases, the corresponding AR solar wind exhibits higher magnetic field strength, charge states, helium abundance (A_He), and first ionization potential (FIP) bias. Our results demonstrate that complex ARs are more effective at generating solar wind. Additionally, the strong magnetic fields and frequent magnetic activities in complex ARs can heat the plasma to higher temperatures and effectively transport helium-rich materials from the lower atmosphere to the upper corona.

Figures (10)

• Figure 1: The yearly numbers and proportions of different types of ARs and AR solar wind. The panel (a) represents the annual number of three types of ARs, and the panel (b) represents the yearly samples of the different types of AR solar wind. The bottom panel represents the annual proportions of each type of AR (panel (c)) and the annual proportions of three types of AR solar wind (panel (d)). The blue, orange and green represent $\alpha$, $\beta$, and complex ARs (panels (a) and (c)) and AR solar wind (panels (b) and (d)). The shaded area represents the annual sunspot numbers. The numbers and proportions of different types of ARs and AR solar wind show clear variations in response to solar activity.
• Figure 1: Panels (a), (b), and (c) show the histogram comparisons of $O^{7+}/O^{6+}$, $Q_{Fe}$, and FIP bias for all AR solar wind before and after the ACE/SWICS anomaly, respectively. The dashed lines indicate the corresponding mean values.
• Figure 2: The top, middle, and bottom rows respectively present the statistical results of the latitudinal distributions of all $\alpha$, $\beta$, and complex ARs from 1999 to 2020. The first column shows the temporal evolution of latitudes for the three types of ARs. The second column compares the latitudinal histograms of the three types of ARs during SC 23 (red) and SC 24 (blue). The third column presents the cumulative distribution function (CDF) curves of the latitudinal distributions for the same types of ARs between the two solar cycles, along with the results of the two sample Kolmogorov-Smirnov (K-S) test. The black vertical dotted line indicates the point where the maximum vertical deviation between the two curves, and the D is the difference between the two curves at that point. The results indicate that the latitudinal distributions of the three types of ARs are very similar, with no significant differences. Moreover, the latitudinal distributions of the same type of ARs are also similar between SC 23 and SC 24.
• Figure 3: The footpoint magnetic field strengths of $\alpha$, $\beta$, and complex AR solar wind during SCs 23 and 24. The first row shows the histograms of footpoint magnetic field strengths of the three types of AR solar wind during SC 23 (red) and SC 24 (blue). The second row presents the CDF curves of footpoint magnetic field strengths for different types of AR solar wind, combining data from SC 23 and SC 24, along with the two sample K-S test results between any two groups. The cyan, yellow, and black curves represent $\alpha$, $\beta$, and complex AR solar wind, respectively. The third row compares the CDF curves of footpoint magnetic field strengths for $\alpha$, $\beta$, and complex AR solar wind between SC 23 and SC 24. The footpoint magnetic field strength of complex AR solar wind is significantly higher than that of the other two types of AR solar wind.
• Figure 4: The in-situ magnetic field strengths of $\alpha$, $\beta$, and complex AR solar wind. The layout is the same as Figure \ref{['footpoint']}. The higher the magnetic complexity of the AR, the higher the in-situ magnetic field strength of the solar wind from the AR.