Shibata et al.(1989) Shibata et al.(1989)[PDF file]
The magnetic flux expands horizontally when the magnetic field emerges into the photosphere, because the velocity is estimated by assuming that the kinetic energy is equal to the magnetic energy. Lifetime ~ 10-30min, Velocity ~ 10km/s(sound velocity) The velocity was estimed: rho v^2 ~ B^2/(8pi) ... kinetic energy is balanced to magnetic energy : Pv^2/Cs^2 ~ B^2/(8pi) (rho=P/Cs^2) v^2 ~ B^2/(8pi P) Cs^2 ~ 1/beta Cs^2 ---> mistake ? Now let's think what has determined the expand velocity ? Next figure is hint ??? grad B^2/(8pi) + grad rho v^2 + grad P + rho g + B^2/(4pi R) = constant
By means of magnetohydrodynamic simulations, we study nonlinear evolutions of the magnetic buoyancy instability such as the Parker instability in a gravitationally stratified magnetized gas layer. You will set up initial conditions for the Galaxy or for the Sun, and simulate the growth of the instability. We discuss how the magnetic loops created by the instability will actually be observed.
