Travel-Time Analyses of an Emerging-Flux Region

摘要

Travel-time analyses of a newly-formed plage region are presented. The dataset has been obtained from the 12-hr Hinode observation of an emerging-flux region (to be NOAA AR 10975) close to the disc center on 23 November 2007. The SOT provides data in Ca ii H line and in Fe t 557.6nm line; we use both chromospheric intensity oscillation data and photospheric Dopplergrams for travel-time measurement by a cross-correlation method. In the plage region, we have detected a travel-time anomaly in the chromospheric data, but not in the photospheric data. This can be interpreted as a signature of downflows in the chromosphere. This result illustrates how time-distance techniques can be used to study chromospheric flows.