Solar Transients and Space Weather (STSW)

Science Highlights

Propagation of waves from the photosphere to the chromosphere in & around plage

In the traditional view of the solar atmosphere, 5-minute p-mode oscillations should not propagate upward because the acoustic cutoff is at periods of 3 minutes. However, it has long been known that p-mode oscillations propagate upward in and around magnetic flux concentrations. Several mechanisms have been proposed to explain this upward propagation of oscillations that have frequencies below the canonical values for the cut-off frequency in the photosphere, e.g., leakage along inclined field lines, or radiative losses in the photosphere. Recently, the advent of higher resolution observations and modeling have led to renewed interest in this topic, with suggestions that p-mode leakage can lead to formation of spicules. Our results show that waves with 5-minute periods are found to propagate only at the periphery of the plage, and only in the direction in which the field can be reasonably expected to expand. de Wijn, McIntosh & De Pontieu (2009) concluded that field inclination is critically important in the leakage of p-mode oscillations from the photosphere into the chromosphere.

Figure caption: Phase difference between Doppler shift in Fe I and Na I D1 at 3.3 mHz. Blue and red respectively indicate positive and negative phase difference, i.e., upward and downward propagation. Contours indicate the average Stokes V signal in Fe I at 2.5% intervals. Arrows in the bottom left corner of each panel indicate the shift between Na I D1 and Fe I using Na I D1 as reference. Rows are shifted in north by 3, 0, and −3 Hinode SOT/NFI pixels of 0.16", respectively from top to bottom. Columns are shifted east by 3, 0, and −3 NFI pixels, respectively from left to right.