M. Stangalini, F. Giannattasio, D. Del Moro, F. Berrilli
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 fact could be due to a complex interaction of many
processes: opacity effects, MHD mode conversion and intrinsic reduced acoustic
emissivity in strong magnetic fields. While five-minute oscillations are the
dominant component in the photosphere, it has been shown that chromospheric
heights are in turn dominated by three-minute oscillations. Two main theories
have been proposed to explain their presence 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 and that their amplitude depends on the magnetic
field strength and is strictly confined in the umbral region.
View original:
http://arxiv.org/abs/1202.1384
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