Scattering polarization of hydrogen lines in the presence of turbulent electric fields

We study the broadband polarization of hydrogen lines produced by scattering of radiation, in the presence of isotropic electric fields. In this paper, we focus on two distinct problems: a) the possibility of detecting the presence of turbulent electric fields by polarimetric methods, and b) the influence of such fields on the polarization due to a macroscopic, deterministic magnetic field. We found that isotropic electric fields decrease the degree of linear polarization in the scattered radiation, with respect to the zero-field case. On the other hand, a distribution of isotropic electric fields superimposed onto a deterministic magnetic field can generate a significant increase of the degree of magnetic-induced, net circular polarization. This phenomenon has important implications for the diagnostics of magnetic fields in plasmas using hydrogen lines, because of the ubiquitous presence of the Holtsmark, microscopic electric field from neighbouring ions. In particular, previous solar magnetographic studies of the Balmer lines of hydrogen may need to be revised because they neglected the effect of turbulent electric fields on the polarization signals. In this work, we give explicit results for the Lyman α and Balmer α lines. PACS numbers: 32.60.+i, 32.80.Bx, 52.25.Os ‡ Now at the Instituto de Astrof́ısica de Canarias, Vı́a Láctea s/n, E-38200 La Laguna, Tenerife, Spain § The National Center for Atmospheric Research is sponsored by the National Science Foundation Hydrogen polarization in turbulent electric fields 2 Table 1. Holtsmark normal field strengths of microturbulent electric fields in hydrogen plasmas of laboratory and astrophysical interest. Object N (cm) E (V cm) E (e.s.u.) Interstellar gas 1 3.75 10 1.25 10 Gaseous nebula 10 3.75 10 1.25 10 Solar Corona 10 3.75 10 1.25 10 Solar Corona, solar transition region 10 1.74 5.80 10 Solar Chromosphere, solar prominences 10 8.08 2.69 10 Solar T minimum, diffuse hot plasma 10 3.75 10 1.25 10 Solar Photosphere, gas discharge 10 8.08 10 2.69 Thermonuclear plasma 10 3.75 10 1.25 10 Dense hot plasma 10 3.75 10 1.25 10 Laser plasma 10 8.08 10 2.69 10