On the influence of magnetic fields on level populations |
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| Authors: | Z Q Qu C L Xu X Y Zhang X L Yan C L Jin |
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| Institution: | Yunnan Astronomical Observatory/National Astronomical Observatories, Chinese Academy of Sciences, Kunming 650011, China;Max-Planck-Institute for Solar System Research (MPS), Max-Planck Street 2, D-37191 Katlenburg-Lindau, Germany;Graduate School of the Chinese Academy of Sciences, Zhongguancun, Beijing 100036, China |
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| Abstract: | The influence of magnetic fields on the energy level populations of atoms is firstly studied by analysing the Stokes profiles of Fe i 6302.5 forming in the solar magnetized atmosphere, with the aid of a departure factor defined to evaluate the deviation from the normal Boltzmann distribution without a magnetic field. This factor is directly related to the ratio of line-source function to the continuum one. The relationship between the departure and the magnetic field reveals an effect that the magnetic field induces an exponential increase in the level population of the lower level of Fe i 6302.5 (Landé factor g = 2.5 ) with the field strength. This indicates that the magnetic field can cause the redistribution of populations of those levels whose Landé factors are non-zero. Therefore, this effect should be included in the calculation of the statistical equilibrium. Secondly, an experiment utilizing the Hg5461 line in the laboratory on the Earth is carried out to reveal that the exponential relation is independent of variations in temperature, and the excitation is completely magneto-induced. Finally, the exponential relation is explained by taking account of the magnetic energy in the Boltzmann distribution. |
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| Keywords: | atomic processes line: formation polarization radiation mechanisms: non-thermal radiative transfer Sun: magnetic fields |
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