K-GRAINS AS A 3-DIMENSIONAL PHENOMENON .2. PHASE-ANALYSIS OF THE SPATIOTEMPORAL PATTERN

We have observed spatially one- and two-dimensional time series(1) of Ca II K spectra to study the spatio-temporal excitation pattern of the Ca K-2V grains. We compare the phases of chromospheric velocity fluct uations (V) measured in K-3 with those of spectral brightness measured at fixed wavelength intervals in K-2V and K-2R (I). Temporal crosscor relation functions of prominent chromospheric (3 min) wavetrains repro duce the commonly observed coincidence of brightness maxima in K-2V an d extreme redshift of Ks, whereas the corresponding V-I phases in the k - v diagrams reveal a distinct dichotomy: Only in the gaps between t he p-mode ridges do the spectra exhibit homogeneous areas with a stabl e phase of approximately 180 degrees in agreement with the crosscorrel ation result. On the ridges the V-I phase switches to distinctly lower values near -90 degrees, with K-3 redshift preceding K-2V brightening . The latter value is similar to the characteristic V-I phase measured in the core of other chromospheric lines. Our findings support the co ntention that a) K-grains are excited by superposition of resonant p-m odes, and b) that p-modes exhibit a uniform signature of their dynamic behaviour throughout the full height range of the chromosphere.