A MHS model in the solar corona

Since direct measurements of the solar coronal magnetic field and plasma are extremely difficult and inaccurate, we use a modeling approach based on observational quantities, e.g. the measured photospheric magnetic field, to reconstruct the structure of the global solar corona.An analytic magnetohydrostatic (MHS) model (Neukirch 95) was taken to extrapolate the magnetic field in the corona from photospheric magnetic field measurement from the Wilcox Solar Observatory. The boundary conditions are given by a synoptic magnetogram on the photosphere and by a source surface at the outer boundary. In the model, the electric current density was decomposed into two components: one component is aligned with the magnetic field lines, whereas the other component flows in spherical shells. The second component of the current generates finite Lorentz forces, which are balanced by the plasma pressure gradient and the gravity force. So the 3D distribution of the magnetic field and plasma can be derived self-consistently in one model. The magnetic field distribution of our model differs noticeably from both potential and force-free field models for the same boundary conditions. The plasma density in the MHS model is higher in the equatorial plane than in the polar region, which gives a reasonable result.