Solar photosphere magnetization
Résumé
In an observation review published in Solar Physics in 2018, H. Balthasar shows that observations with different telescopes, spectral lines, and interpretation methods all agree about a vertical magnetic field gradient in solar active regions on the order of 3 G/km, when the horizontal magnetic field gradient is found of 0.3 G/km only. This represents an inexplicable discrepancy with respect to the divB=0 law. The objective of this poster is to explain these observations through the law B=µ0(H+M) in magnetized media. Magnetization is due to the plasma diamagnetism, which results from the spiral motion of free electrons or charges about the magnetic field. Their usual photospheric densities lead to very weak magnetization M, four orders of magnitude smaller than H. It is then assumed that electrons escape from lower layers where their thermal velocity is much larger than the escape velocity, in a quasi-static spreading, and accumulate in the photosphere, where they are also finally retained by the lower-lying protons. By evaluating the magnetic energy of the microscopic atom embedded in the magnetized medium obeying the macroscopic law B=µ0(H+M), it is shown that the Zeeman hamiltonian is due to the effect of H. Thus, what is measured is H. The decrease of the density with height is responsible for non-zero divergence of M, which is compensated for by the divergence of H, in order to ensure divB=0.