Extraction of Photospheric and Chromospheric Bright Regions and aSunspot Using Fuzzy C-Means Clustering and Region Growing Methods

Abstract:

Solar upper photosphere and chromosphere are covered by magnetic bright regions. Some of these
regions are magnetic networks that appeared near sunspots called plage. Also, sunspots are considered
as a criterion of solar magnetic activity. Here, the Fuzzy C-Means Clustering algorithm and the function
of the region grow are used to segregate bright regions and a sunspot from 1600 and 1700 Å images
taken by Solar Dynamic Observatory (SDO)/Atmospheric Imaging Assembly (AIA). We extracted
the intensity fluctuations of bright regions, and also, the size of bright regions and the sunspot (with
NOAA 12526) for three days (2016 March 30-2016 April 01) with a time lag of six minutes in
the square area near the solar disk. This box is selected with an area of 380 × 380 pixels(region centered
with longitudes ±115″ around the central meridian, and the latitudes surrounded by ±115″ around
the equator) to reduce the projection effects (Figure 1). The mean size for the sunspot is obtained to
be in the range of 2100-2200 Mm2 at both channels. The time series of areas covered by bright
regions at 1600 and 1700 Å around the sunspot show the strong positive correlation. The mean
brightness fluctuations of bright regions are about 0.15. In the future, we aim to study statistically
the morphological properties of sunspots and bright regions that appeared around the sunspots for
finding a relationship between the evolution of sunspots and surrounded bright regions.