IS THERE AN ACOUSTIC-RESONANCE IN THE SOLAR CHROMOSPHERE

By comparing helioseismology data from 1986, 1988, and 1989 we have found that the frequency dependence of the frequency perturbation of solar p-modes caused by solar activity drops abruptly for modes of frequency above almost-equal-to 3.9 mHz. The drop in the frequency dependence of the frequency shift may result from solar cycle changes in the chromosphere, provided that the chromosphere acts as a cavity in which p-modes are trapped (Goldreich et al.). We find no evidence in the temporal power spectrum of a time series of narrow-band Ca II K-line filtergrams of a resonance which would reveal the existence of a chromospheric cavity. This circumstance constrains the possible physical explanations of the frequency shifts.