Presentation Information
[O12-P94]Magnetic Energy Release Driven by the Flare–CME Connection
*Shota Saragai1 (1. Musashi High School)
Keywords:
Solar Flares,Coronal Mass Ejections,Magnetic Reconnection
Background and Objectives
Solar flares and coronal mass ejections (CMEs) are major phenomena of magnetic energy release on the Sun. Flares involve electromagnetic radiation through magnetic reconnection, while CMEs involve plasma eruptions. Flares are often associated with kink instabilities that can trigger torus instabilities, leading to eruptive flares with CMEs. Although various models have been proposed to explain these events, it is still unclear which mechanism is dominant. This study aims to clarify the process of magnetic energy release by examining the relationship between flares and CMEs.
Methodology
Based on the Hinode Flare Catalog [1] and the SOHO CME Catalog [2], an eruptive flare was defined as a flare of higher than C8-class where a CME occurred within the same active region within an hour. For the 969 identified eruptive flares, parameters such as flare duration, peak flux, CME average ejection velocity, mass of CME, and the respective energies were tabulated.
Flare energy was calculated by linear approximation of the temporal evolution of the X-ray flux. Furthermore, since the velocity of small-scale CMEs occurring near the center of the solar disk tends to be underestimated due to line-of-sight effects, the bottom 15% of the data after regression correction were excluded as outliers.
Result 1: Energy Relationship
The relationship between flare and CME energy is shown in Fig 1. It was found that CME energy increases with a non-linear correlation relative to flare energy.
The top 25% of the data were well-approximated by a power law with an index of 1.198±0.008 (R = 0.521). However, the bottom 25% exhibited large variance, and no significant approximation was obtained.
Result 2: CME Velocity and Mass
The relationship between flare energy and the average velocity and mass of CMEs is shown in Fig 3. The results revealed that CME mass exhibits a relatively stronger correlation with flare energy compared to CME velocity (R = 0.449 and 0.482, respectively).
Discussion 1: Magnetic Reconnection Process
Flare energy is proportional to Lrec2Delta, where Lrec is the local length and Delta is the region width. Additionally, magnetic energy is proportional to L3, where L is the lobe length.
Assuming there are no significant differences in magnetic field strength across events and that CME energy release efficiency depends primarily on the fraction of free magnetic energy, the global relationship likely depends on spatial scales.
Assuming Lrec is proportional to L, the index of 1.20 observed in the top-tier data can be achieved if Delta is proportional to L0.50. Since Delta is considered to be on the inner layer thickness, this supports the Sweet-Parker model of reconnection (Parker (57)). This suggests that for high-energy events (>1029 erg), magnetic reconnection via plasmoid instability based on the Sweet-Parker model is occurring.
For the lower-tier data (~1028 erg), the dependence on length is smaller, suggesting that another mechanism enhances the amount of released energy, possibly collisionless reconnection based on the Petschek model.
Discussion 2: CME Energy Release Process
From the above discussion, CME energy can be estimated as the independent variable, with average eruption velocity as the dependent variable. Assuming uniform density, the spatial scale provided by energy and the magnetic field corresponds to the scale per mass. Since this correlates well with flare energy, it is inferred that lobe length is more dominant than magnetic field strength in determining energy.
Conclusion
The results suggest that for magnetic reconnection on the Sun, plasmoid instability operates at high energy levels, while collisionless reconnection may operate at moderate levels. Furthermore, we conclude that spatial scale is the dominant factor in determining CME energy.
References
[1] Watanabe, K. et al., 2012, Solar Phys., 279, 317.
[2] Gopalswamy, N. et al., 2024, arXiv, arXiv:2407.04165.
Solar flares and coronal mass ejections (CMEs) are major phenomena of magnetic energy release on the Sun. Flares involve electromagnetic radiation through magnetic reconnection, while CMEs involve plasma eruptions. Flares are often associated with kink instabilities that can trigger torus instabilities, leading to eruptive flares with CMEs. Although various models have been proposed to explain these events, it is still unclear which mechanism is dominant. This study aims to clarify the process of magnetic energy release by examining the relationship between flares and CMEs.
Methodology
Based on the Hinode Flare Catalog [1] and the SOHO CME Catalog [2], an eruptive flare was defined as a flare of higher than C8-class where a CME occurred within the same active region within an hour. For the 969 identified eruptive flares, parameters such as flare duration, peak flux, CME average ejection velocity, mass of CME, and the respective energies were tabulated.
Flare energy was calculated by linear approximation of the temporal evolution of the X-ray flux. Furthermore, since the velocity of small-scale CMEs occurring near the center of the solar disk tends to be underestimated due to line-of-sight effects, the bottom 15% of the data after regression correction were excluded as outliers.
Result 1: Energy Relationship
The relationship between flare and CME energy is shown in Fig 1. It was found that CME energy increases with a non-linear correlation relative to flare energy.
The top 25% of the data were well-approximated by a power law with an index of 1.198±0.008 (R = 0.521). However, the bottom 25% exhibited large variance, and no significant approximation was obtained.
Result 2: CME Velocity and Mass
The relationship between flare energy and the average velocity and mass of CMEs is shown in Fig 3. The results revealed that CME mass exhibits a relatively stronger correlation with flare energy compared to CME velocity (R = 0.449 and 0.482, respectively).
Discussion 1: Magnetic Reconnection Process
Flare energy is proportional to Lrec2Delta, where Lrec is the local length and Delta is the region width. Additionally, magnetic energy is proportional to L3, where L is the lobe length.
Assuming there are no significant differences in magnetic field strength across events and that CME energy release efficiency depends primarily on the fraction of free magnetic energy, the global relationship likely depends on spatial scales.
Assuming Lrec is proportional to L, the index of 1.20 observed in the top-tier data can be achieved if Delta is proportional to L0.50. Since Delta is considered to be on the inner layer thickness, this supports the Sweet-Parker model of reconnection (Parker (57)). This suggests that for high-energy events (>1029 erg), magnetic reconnection via plasmoid instability based on the Sweet-Parker model is occurring.
For the lower-tier data (~1028 erg), the dependence on length is smaller, suggesting that another mechanism enhances the amount of released energy, possibly collisionless reconnection based on the Petschek model.
Discussion 2: CME Energy Release Process
From the above discussion, CME energy can be estimated as the independent variable, with average eruption velocity as the dependent variable. Assuming uniform density, the spatial scale provided by energy and the magnetic field corresponds to the scale per mass. Since this correlates well with flare energy, it is inferred that lobe length is more dominant than magnetic field strength in determining energy.
Conclusion
The results suggest that for magnetic reconnection on the Sun, plasmoid instability operates at high energy levels, while collisionless reconnection may operate at moderate levels. Furthermore, we conclude that spatial scale is the dominant factor in determining CME energy.
References
[1] Watanabe, K. et al., 2012, Solar Phys., 279, 317.
[2] Gopalswamy, N. et al., 2024, arXiv, arXiv:2407.04165.