Morphology and evolution of coronal holes at the wavelengths of 171 Å, 193 Å, and 211 Å in the Solar Cycle 24

Abstract

Coronal holes are an area that appears dark in the corona, which is observable in EUV and X-ray wavelengths. This area has an open magnetic field structure. The magnetogram image showed that the coronal hole has one polarity (unipolar). Commonly, the shape and size of the coronal hole at the poles are related to the structural strength of the magnetic field. Because of this unipolar nature, the coronal hole becomes a source of the high-speed solar wind, which can cause a geomagnetic storm. The number, size, and position of the coronal hole vary as a function of the solar cycle, with the reversal of magnetic polarity every 11 years. The characteristics of the coronal hole will be different at the maximum and minimum phases of the solar cycle. Aims of this study are to determine the morphology of coronal hole based on the area, magnetic field strength, open magnetic flux, and the evolution of the coronal hole according to latitude during minimum solar activity (or spotless days) and maximum at the Solar Cycle 24. The method applied in this study is CHIMERA (Coronal Hole Identification via Multi-thermal Emission Recognition Algorithm). There are relations between magnetic field strength and magnetic flux with areas of coronal holes from September 2010 to May 2019 that follow the exponential and linear distributions.