Scattering Polarisation of the d-States of Ions and Solar Magnetic Field: Effects of Isotropic Collisions

Abstract

Analysis of solar magnetic fields using observations as well as theoretical interpretations of the scattering polarization is commonly designated as a high priority area of the solar research. The interpretation of the observed polarization raises a serious theoretical challenge to the researchers involved in this field. In fact, realistic interpretations need detailed investigations of the depolarizing role of isotropic collisions with neutral hydrogen.The goal of this paper is to determine new relationships which allow the calculation of any collisional rates of the d-levels of ions by simply determining the value of n * and Ep without the need of determining the interaction potentials and treating the dynamics of collisions. The determination of n * and Ep is easy and based on atomic data usually available online. Accurate collisional rates allow a reliable diagnostics of solar magnetic fields.In this work we applied our collisional FORTRAN code to a large number of cases involving complex and simple ions. After that, the results are utilized and injected in a genetic programming code developed with C-langugae in order to infer original relationships which will be of great help to solar applications. We discussed the accurarcy of our collisional rates in the cases of polarized complex atoms and atoms with hyperfine structure. The relationships are expressed on the tensorial basis and we explain how to include their contributions in the master equation giving the variation of the density matrix elements.As a test, we compared the results obtained through the general relationships provided in this work with the results obtained directly by running our code of collisions. These comparisons show a percentage of error of about 10% in the average value. Our results could be implemented easily in numerical codes concerned with the simulations of the scattering polarization to obtain accurately the magnetic field in the quiet Sun.

Collisions of Electrons with Alkali, Alkaline and Complex Atoms Relevant to Solar and Stellar Atmospheres

“…Next, we concentrate on the polarization transfer rates D k (J → J ) obtained in the tensorial basis and fundamental for spectro-polarimetric studies where k is the tensorial order. Full details about the D k (J → J ) and the use of the tensorial basis for polarization studies can be found in the papers by [1,[10][11][12]14,28,29,[31][32][33][34][35].…”

“…Let us consider an isotope of an atom with nuclear spin I and the total angular momentum of a hyperfine structure F = J + I. [35] provided a detailed discussion regarding the direct and indirect methods to calculate collisional hyperfine rates.…”