κH-mechanism of a self-consistent solar eruption
We report on a new magnetohydrodynamic simulation for the sequence evolution of a magnetic field from emergence
to eruption on the Sun. The magnetic field in the shape of a twisted flux tube emerging below the solar surface
forms a pre-eruptive structure in the corona, which is composed of expanding envelop flux and a quasi-static inner
core called flux rope; this inner core eventually seems to erupt. The evolution proceeds self-consistently; that is,
any preexisting coronal magnetic field that causes additional side effects on the evolution of the emerging magnetic
field is not assumed. This highlights a possible eruption mechanism inherent in the dynamic nature of the emerging
magnetic field. The mechanism is characterized by two key quantities: the curvature (κ) and the scale height (H)
of the emerging magnetic field (Magara 2013).
We study the stability and dynamics of a flux rope formed through the emergence of a twisted magnetic flux tube
into the solar atmosphere. A three-dimensional magnetohydrodynamic simulation has been performed to investigate
several key factors affecting the dynamics of the flux rope. The stability of the flux rope is examined by deriving
the decay index of the coronal magnetic field surrounding the flux rope. We investigate a transition between the
quasi-static and dynamic states of the flux rope through an analysis of the curvature and scale height of emerging
magnetic field. A practical application of this analysis for global eruptions is also considered (An & Magara 2013).
Reference
Magara, T. 2013, PASJ, 65, L5
An, J. M. & Magara, T. 2013, ApJ, 773, 21
