Speaker
Description
In this presentation I summarize my early-science paper, where we report on the direct measurement of the height dependence of $p$-mode phase shifts in the lower solar atmosphere.
The line-core positions of 19 spectral lines in a 2 nm-wide window around the Ca II H line (396.8 nm) were used to determine the vertical oscillations at their respective formation heights. We find that the phases of the oscillations of the line core positions are roughly ordered according to the computed formation heights of the respective spectral lines. A statistical study of the phase shifts using the 1-hour-long sit-and-stare observation reveals that waves propagating upwards from the photosphere to heights of approximately 500--700 km are most common, with average time lags of 20--30 s. Also present are evanescent waves with zero phase shifts, predominantly above intergranular lanes and areas of enhanced magnetic activity. Additionally, downward propagating waves with negative time lags of 10--15 s are seen, mostly above areas of enhanced magnetic activity. A common feature of all the observed $p$-mode waves is that in the lower 250 km they show small time lags of zero to a few seconds, and only at higher layers the propagating waves become more dominant.