Analyzing Magnetic Free Energy Estimates: Insights into Coronal Energy Release Dynamics
This session recap from May 1998 focuses on comparing estimates of magnetic free energy in AR 8210 to enhance our understanding of coronal energy release. A significant finding indicated that the estimated coronal energy loss during a magnetogram interval was around 1e+31 erg. Key lessons include differentiating between free magnetic energy and usable energy, recognizing the roles of reconnection in dissipating energy, and understanding the complexities of estimating magnetic energy. Emphasis was also placed on the variability in potential field calculations and the unclear relationship between free energy and coronal emission.
Analyzing Magnetic Free Energy Estimates: Insights into Coronal Energy Release Dynamics
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Presentation Transcript
May 1998 “Pre-Event” Session Recap GOAL: compare estimates of magnetic free energy in AR 8210, to improve our understanding of coronal energy release. Coronal energy loss estimate during magnetogram interval: <~1e+31 erg
Lessons Learned • We distinguished between free magnetic energy, and “usable” free magnetic energy. • Through reconnection, flares probably dissipate current sheets, not volume currents. So the “free energy” stored in volume currents isn’t “usable.” (CMEs might differ in this regard?) • MCC claims to estimate only current sheet energies, while NLFFF / Virial include volume currents. • Hence, MCC = lower bound, & NLFFF/Virial = upper bound? Our coronal energy loss estimates fell between these two.
Lessons Learned, cont’d: • Many versions of “the” potential field matching a given Bn exist, and can differ substantially in energy. • Some standardization would be desirable. • The relationship between free magnetic energy & coronal emission is not obvious. • It’s not clear that a measured increase in free energy should result in subsequent energy release immediately.