Does the ion cyclotron exist in the inner corona?

Abstract

The present work is about the interpretation of the linear polarization of the O {vi} D_2 (lambda1032 ) coronal line observed by SUMER/SoHO. We take into account the effect of the Doppler redistribution due to the scattering ions motion. We consider the cases of isotropic and anisotropic velocity field distributions. The latter can be interpreted by the ion-cyclotron effect that affects heavy ions in the solar corona. The comparison of the numerical results with the observations yields constraints on the solar wind outflow speed and on the velocity field distribution of the O⁵⁺ ions at low coronal altitudes in the polar holes.