ELEMENT SEGREGATION IN THE SOLAR CHROMOSPHERE AND THE FIP BIAS - THE SKIMMER MODEL

A new approach of the segregation between high-Fip (First ionisation p otential) and low-Fip elements in the solar chromospheric plateau is p roposed. Magnetic fields emerging from the photosphere up to the chrom osphere and corona can lift up enough low-Fip elements to explain loca lly their observed overabundances. While the magnetic field rises in t his partially ionised medium, the electrons become trapped along the r ising magnetic lines. Protons and ionised heavy (low-Fip) elements fol low due to the induced electric field. The whole bulk of chromospheric gas is eventually brought up due to collisions and charge-exchange pr ocesses. The time delay between the motion of the ionised atoms and th e motion of the whole gas is however sufficient for ions to accumulate in a small frontward layer, in which the chemical composition becomes of ''coronal type'' namely with an overabundance of low-Fip elements. Local overabundances of low-Fip elements are obtained without any mas s bias and within short enough time scales. Helium is expected to be s lightly depleted compared to hydrogen as observed. We present here pre liminary computations using the homogeneous and static chromospheric m odels of Vernazza, Avrett and Loeser 1981. Complete dynamical models s hould be studied in the future, according to the various coronal sites . The present results seem promising enough to motivate further comput ations.