Abstract:
The century long
(
1914
–
2007
)
a
H
(
656.28 nm
)
spectroheliograms from the Kodaikanal Solar Observatory
(
KSO
)
have been recently digitized. Using these newly calibrated, processed images we study the evolution of dark
elongated on-disk structures called
fi
laments, which are potential representatives of magnetic activities on the Sun.
To our knowledge, this is the oldest uniform digitized data set with daily images available today in
a
H
.We
generate Carrington maps for the entire time duration and try to
fi
nd the correlations with maps of the same
Carrington rotation from the Ca
II
K KSO data. Filaments are segmented from the Carrington maps using a semi-
automated technique and are studied individually to extract their centroids and tilts. We plot the time-latitude
distribution of the
fi
lament centroids, producing a butter
fl
y diagram which clearly shows the presence of poleward
migration. We separate polar
fi
laments for each cycle and try to estimate the delay between the polar
fi
lament
number cycle and the sunspot number cycle peaks. We correlate this delay with the delay between polar reversal
and sunspot number maxima. This provides new insight on the role of polar
fi
laments on polar reversal.
