2-D and 3-D Magnetohydrodynamics Simulation of the Solar Emerging Flux

Satoshi Nozawa and Kunio Takahashi

We study the nonlinear magnetohydrodynamics (MHD) simulation of solar
magnetic flux emerging from the convection zone into the photosphere/
chromosphere and corona.  The emerging process of the magnetic flux
initiated by the magnetic buoyancy instability (i.e.,
convective-Parker instability) is studied using a two or three
dimensional MHD code.  We find the following: (1) In 3-D simulation
the magnetic flux expands horizontally when the magnetic field emerges
small into the photosphere. The distribution of magnetic pressure
tends to be in a state of magnetohydrostatic equilibrium.  (2) In 2-D
simulation an initially weak convection zone magnetic flux (~600G) is
amplified up to ~1000 -- 1500 G by the convective collapse of the flux
tube triggered by downflow along the tube in a very short time (< 30
min) after emerging into the photosphere by taking into account the
radiative cooling and the static heating. And the convection zone of
our simulation is has the continues convective motions, therefore we
think the reconnection is occur in the convection zone.