Three-minute wave enhancement in the solar photosphere
Dipartimento di Fisica, Universitá di Roma Tor Vergata, via della Ricerca Scientifica 1, 00133 Rome, Italy
Received: 15 December 2011
Accepted: 6 February 2012
It is a well-known result that the power of five-minute oscillations is progressively reduced by magnetic fields in the solar photosphere. Many authors have pointed out that this could be due to a complex interaction of many processes: opacity effects, MHD mode conversion, and intrinsically weaker acoustic emissivity in strong magnetic fields. While five-minute oscillations predominate in the photosphere, it has been shown that in the chromosphere three-minute oscillations are more common. Two main theories have been proposed to explain the presence of the latter oscillations based upon resonance filtering in the atmospheric cavity and non-linear interactions. In this work, we show, through the analysis of IBIS observations of a solar pore in the photospheric Fe I 617.3 nm line, that three-minute waves are already present at the height of formation of this line, their amplitude depends on the magnetic field strength, and they are strictly confined to the umbral region.
Key words: Sun: oscillations / Sun: helioseismology / Sun: photosphere / sunspots
© ESO, 2012