Calcium Ii Phase Relations and Chromospheric Dynamics

Velocity-velocity and velocity-intensity phase relations from radiative-hydrodynamics calculations by Carlsson & Stein (1992, 1994) are compared with spatially resolved internetwork observations of the H, K, 8498 A, 8542 A and 8662 A lines of ionized calcium. Several of the computed phase relations agree with observations even though the simulations are dominated by propagating shock waves and the observations have been interpreted as evidence for standing waves in the chromosphere. In particular, V(8542) { V(8498) is close to zero in agreement with observations in spite of a factor of nine diierence in opacity. This is explained as due to the Doppler shift of the 8498 line core not being a measure of the velocity at the line core formation height. V(3968) { V(8542) shows a propagating signature contrary to recent observations (Fleck et al., 1994). We speculate that part of the discrepancy is due to depth-dependent microturbulence and eeects of seeing, limited instrument resolution and scattered light. The velocity-intensity phase diierence is close to ?100 degrees both for the 8542 line and the H-line for a variety of input atmospheres and velocity elds. This is due to the dominance of scattering in the source function which leads to a decoupling from the local temperature. The core intensity of the Ca II lines is thus not a good proxy for the local temperature.