J/A+A/601/A106 Sunspot on 1921-2011 (Mandal+, 2017)
Kodaikanal digitized white-light data archive (1921-2011):
Analysis of various solar cycle features.
Mandal S., Hegde M., Samanta T., Hazra G., Banerjee D., Ravindra B.
<Astron. Astrophys. 601, A106 (2017)>
=2017A&A...601A.106M 2017A&A...601A.106M (SIMBAD/NED BibCode)
ADC_Keywords: Sun
Keywords: Sun: activity - sunspots - Sun: magnetic fields - Sun: photosphere -
catalogs
Abstract:
Long-term sunspot observations are key to understanding and predicting
the solar activities and its effects on space weather. Consistent
observations, which are crucial for long-term variations studies, are
generally not available due to upgradation/modification of
observatories over the course of time. We present data for a period of
90 yr acquired from persistent observation at the Kodaikanal
observatory in India.
We aim to build a uniform sunspot area time series along with their
positions for a 90-yr period between 1921 and 2011, as obtained from
the newly digitized and calibrated white-light images from the
Kodaikanal observatory. Our aim is to compare this new time series
with known sources and confirm some of the earlier reported results
with additional new aspects.
We use an advanced semi-automated algorithm to detect the sunspots
form each calibrated white-light image. Area, longitude and latitude
of each of the detected sunspots are derived. Implementation of a
semi-automated method is extremely necessary in such studies as it
minimizes the human bias in the detection procedure.
Daily, monthly, and yearly sunspot area variations, obtained from the
Kodaikanal, compared well with the Greenwich sunspot area data. We
find an exponentially decaying distribution for the individual sunspot
area for each of the solar cycles. Analyzing the histograms of the
latitudinal distribution of the detected sunspots, we find Gaussian
distributions, in both the hemispheres, with centers at ∼15°
latitude. The height of the Gaussian distributions are different for
the two hemispheres for a particular cycle. Using our data, we show
clear presence of Waldmeier effect, which correlates the rise time
with the cycle amplitude. Using the wavelet analysis, we explored
different periodicities on different time scales present in the
sunspot area times series.
Description:
Regular observations at the Kodaikanal observatory began in 1904 using
a white-light telescope with a 10-cm aperture lens and a f/15 light
beam. Between 1912 and 1917, the objective lens was changed several
times and in 1918, a 15-cm achromatic lens was installed. This new
configuration produced a 20.4cm size image of the Sun in the image
plane. Photographic plates were used to capture the image. The same
telescope has been used since 1918 up until 2011 (observations with
this telescope continue to be made even today but those images are yet
to be calibrated and thus they are not part of the data used in this
paper) to take regular white-light observation of the sun.
We present observations from 1921 to 2011.
For quarries, contact Sudip Mandal ()
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
wlarea.dat 52 127770 Kodaikanal White light spotless days data
Time: 1921-2011, Version no: kodaiWLV1.0
spotless.dat 45 4593 Kodaikanal White light spotless days data
Time: 1921-2011, Version no: kodaiWLV1.0
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See also:
VI/138 : Sunspots catalogues, 1853-1870 (Casas+, 2013)
J/A+A/390/707 : Hemispheric Sunspot Numbers 1975-2000 (Temmer+, 2002)
J/A+A/447/735 : Hemispheric Sunspot Numbers 1945-2004 (Temmer+, 2006)
J/A+A/584/A73 : Sunspot areas and tilt angles (Senthamizh Pavai+, 2015)
J/A+A/595/A104 : Scheiner drawing sunspot areas and tilt angles (Arlt+, 2016)
J/A+A/599/A131 : Butterfly diagram wings (Leussu+, 2017)
J/A+A/601/A109 : Monthly numbers of sunspot groups 1749-1996 (Usoskin+, 2017)
Byte-by-byte Description of file: wlarea.dat spotless.dat
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Bytes Format Units Label Explanations
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1- 10 A10 "YYYY/MM/DD" Obs.date Observation date
12- 16 A5 "h:m" Obs.time Observation time
18- 28 F11.7 deg Lon ?=- Minimum longitude
30- 41 F12.8 deg Lat ?=- Minimum Latitude
43- 52 F10.5 --- Area ?=- Area (muHem)
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History:
Copied at https://kso.iiap.res.in/white_light
References:
Ravindra et al., Paper I 2013A&A...550A..19R 2013A&A...550A..19R
(End) Patricia Vannier [CDS] 18-May-2017