HOW MUCH DOES A MAGNETIC FLUX TUBE EMERGE INTO THE SOLAR ATMOSPHERE?

We studied the controlling parameters of flux emergence with a focus on the relation between the configuration of coronal magnetic field and the pre-emeged state of subsurface magnetic field. We performed a series of magnetohydrodynamic simulations (dynamic model) and find an interesting result on the twist of coronal magnetic field, that is, the coronal magnetic field formed via flux emergence actually contains less amount of twist (relative magnetic helicity normalized by magnetic flux) than what is expected in kinematic models for global-scale solar eruptions. Based on this result, we propose another possible mechanism for producing these global-scale solar eruptions.