Seminar at LESIA

Today a seminar for the Solar Physic Group of LESIA, my home group.

Magnetic helicity and its conservation: a future proxy for solar eruption predictions?

PDF version of the seminar

Nowadays, no quantity has been discovered that can be satisfactorily used as an efficient proxy to predict solar flares and eruptions. Solar eruptivity forecast are still mainly based empirical methods based on multiple criterions about the properties of actives regions. In this talk, I’ll present potentially good deterministic predictor of eruption: magnetic helicity.

Magnetic helicity quantifies the geometric properties of the magnetic field such as its level of twisting and braiding. The amount of helicity present in a domain constrains the final stage that a magnetic system can reach by resistive relaxation. It is therefore a key quantity for models of coronal heating and solar/stellar flares. Unlike most quantities, magnetic helicity is one of the few invariant of ideal magnetohydrodynamics, the physical paradigm that governs the evolution of eruptions.

About forty years ago, Taylor hypothesized that helicity is quasi- conserved even when magnetic reconnection develops. Because of the difficulty to properly compute magnetic helicity, this prediction has not yet been satisfactorily demonstrated. Using a state-of-the-art methods to correctly estimate magnetic helicity in a numerical domain I will show the very high-level of conservation of magnetic helicity in a numerical simulation of a solar active event, even though most of the free magnetic energy is dissipated. This pave the way for further studies of a innovative and effective proxy for space weather.

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