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Paper: The Ca II Infrared Triplet Lines as Diagnostics of Chromospheric Magnetism
Volume: 368, The Physics of Chromospheric Plasmas
Page: 139
Authors: Pietarila, A.; Socas-Navarro, H.; Bogdan, T.
Abstract: The Ca II infrared (IR) triplet lines are a promising candidate for studying chromospheric magnetism and dynamics. To study how good of a diagnostic the lines are for chromospheric magnetism in the quiet Sun we have constructed a MHD simulation in the high plasma-β regime, analyzed quiet Sun spectropolarimetric data of the lines and used a non-local thermodynamic equilibrium (nLTE) inversion code on the observations. In the simulation, where shocking acoustic waves dominate the dynamics, the Ca lines show a timevarying pattern of disappearing and reappearing Stokes V lobes. Waves are seen in the observations as well, but the dynamics are more complex. Unlike in the simulation, the observed Ca lines do not have similar shapes and the Stokes V asymmetries are determined by the local magnetic topology, not the phase of the wave. The fundamental differences between the observations and the simulation lead one to conclude that a 1D plane parallel atmosphere is not a valid approximation for the chromosphere. Nor can the effects of magnetic fields on the dynamics be neglected. This is further supported by the inversions failure to reproduce line profile asymmetries caused by gradients in the velocity and/or magnetic field. To explain the asymmetries, 3D structures and strongly localized gradients need to be included. The work presented here will be published in more detail elsewhere.
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