Speaker
Nabil Freij
(University of Balearic Islands)
Description
Ground-based observations have revealed that sunspots and magnetic pores display a
range of oscillations that are observed in cross-sectional area of these structures.
Previous work has demonstrated that these oscillations range from several to tens of
minutes and are interpreted as slow MHD sausage waves. An important property of these
waves is that they are able to channel energy as they propagate upwardly from the
photosphere and into the chromosphere. To achieve these results requires the
accurate contouring of these structures and the amplitude of the observed
oscillations. The current literature has only measured the cross-sectional area of
these magnetic structures using a threshold value from the Quiet-Sun and focused on
ground-based data which, while reduced, still has effects from the Earth's
atmosphere. By making the move to IRIS and Hinode, it allows several improvements
when compared to current literature. With the removal of Earth's atmospheric, seeing
effects which can introduce oscillations are removed and give a cleaner estimate of
the oscillation amplitude. Furthermore, by investigating a range of thresholding
methods details the difficulties and best practices of thresholding sunspots and
magnetic pores.
Primary author
Nabil Freij
(University of Balearic Islands)
