Xavier Bonnin, Jean Aboudarham, Nicolas Fuller, Andre Csillaghy, Robert D. Bentley
We present a new method to automatically track filaments over the solar disk.
The filaments are first detected on Meudon Spectroheliograph Halpha images of
the Sun, applying the technique developed by Fuller, Aboudarham, and Bentley
(2005). This latter combines cleaning processes, image segmentation based on
region growing, and morphological parameters extraction, including the
determination of filament skeletons. The coordinates of the skeleton pixels,
given in a heliocentric system, are then converted in a more appropriate
reference frame that follows the rotation of the Sun surface. In such a frame,
a co-rotating filament is always located around the same position, and its
skeletons (extracted from each image) are thus spatially close, forming a group
of nearby features. In a third time, the shape of each skeleton is compared
with its neighbours using a curve matching algorithm. This step will permit to
define the probability P that two close filaments in the co-rotating frame, are
actually the same one observed on two different images. At the end, the pairs
of features for which the corresponding probability is greater than a threshold
value, are associated using unique tracking identification numbers.\On a
representative sample of filaments, the good agreement between automated and
manual tracking confirms the reliability of the technique to be applied on
large data sets. Especially, this code is already used in the frame of the
Heliophysics Integrated Observatory (HELIO) to populate a catalogue dedicated
to solar and heliospheric features (HFC). An extension of this method to others
filament observations, and possibly the sunspots, faculae, and coronal holes
tracking can be also envisaged.
View original:
http://arxiv.org/abs/1202.2072
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