Solar Phys (2020) 295:120
https://doi.org/10.1007/s11207-020-01691-3
Correlations of Sunspot Physical Characteristics during
Solar Cycle 23
Adriana Valio
1
· Eduardo Spagiari
2
·
Mauricio Marengoni
2
· Caius L. Selhorst
3
Received: 13 October 2019 / Accepted: 16 August 2020
© Springer Nature B.V. 2020
Abstract The behavior of sunspots is governed by the magnetic dynamo acting deep within
the convection zone of the Sun. Therefore, knowledge of sunspot physical characteristics
and how they evolve in time during a solar cycle can help to improve our understanding of
the solar magnetic behavior. This work analyzes the physical characteristics of sunspots dur-
ing the Solar Activity Cycle 23, detected using computer vision techniques. The main goal
is to derive the relationships between sunspot properties. Images in visible light and mag-
netograms of the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric
Observatory (SOHO) were used to detect sunspots and to extract their characteristics such
as area, intensity (or temperature), and magnetic field magnitude. A total of 32,223 sunspots
were analyzed, with longitudes between −40
◦
and 40
◦
, throughout the entire Solar Cycle
23, from May 1996 through April 2008. These spots fell mainly into three categories. Most
sunspots (85%) did not exhibit a well defined umbra, with average intensities larger than
0.657 relative to disk center, which corresponds to temperatures greater than 5200 K. A sec-
ond group comprising less than 12% of the spots, was cooler (temperature less than 5200 K)
and with more intense magnetic fields (2000 – 4000 G) and mostly presented a well de-
fined umbra. Lastly, only 3% of the spots had large areas and strong magnetic fields with
complex umbrae, but intermediate temperatures. The temporal behavior of sunspot physical
characteristics throughout the 11 year cycle and the relationships between them were veri-
B A. Valio
avalio@craam.mackenzie.br
E. Spagiari
e.spagiari@gmail.com
M. Marengoni
mauricio.marengoni@mackenzie.br
C.L. Selhorst
caiuslucius@gmail.com
1
Centre for Radio Astronomy and Astrophysics (CRAAM), Mackenzie Presbyterian University, São
Paulo, Brazil
2
Faculty of Computation and Informatics, Mackenzie Presbyterian University, São Paulo, Brazil
3
NAT, Universidade Cruzeiro do Sul / Universidade Cidade de São Paulo, São Paulo, Brazil