FlNE-SCALE MAGNETIC EFFECTS ON p-MODES AND HIGHER FREQUENCY ACOUSTIC WAVES IN A SOLAR ACTIVE REGION

摘要

We present results from a 5 hr time series of simultaneous high-resolution measurements of oscil- lations in the photosphere and the chromosphere on fine spatial scales for a rapidly evolving solar active region and examine their relation to the vector magnetic field. The photospheric oscillations are deter- mined from Doppler shifts in the Zeeman-insensitive spectral line Fe l 557.6 nm, whereas the chromo- spheric oscillations are determined from the intensity fluctuations seen in the Ca II K line. The vector magnetic field configurations just prior to and just after the time-series measurements are obtained from the full Stokes inversion of the line profiles of Fe I 630.15 and 630.25 nm. In both the photosphere and the chromosphere, p-mode power is suppressed by the magnetic field, decreasing with increasing field strength. At higher frequencies (above the acoustic cutoff power is also suppressed at the highest mag- netic field strengths in the photosphere and the chromosphere but is enhanced in the photosphere in localized patches ("halos") of intermediate field strength surrounding the patches of highest field strength (as first reported by Brown et al.). The evidence for similar halos in the chromosphere (as first seen by Braun et al. and Toner & LaBonte) and their association with the photospheric halos is less clear. We find seismic evidence, in the forms of suppression of p-mode and higher frequency power and a halo of enhanced higher frequency power, for a developing pore prior to its appearance as a dark patch in Fe 1 557.6 nm core intensity. This result shows that p-mode power suppression cannot be due pri- marily to the greater transparency of the cooler pore atmosphere.