The Sun is the most important factor of life on earth. Without the sun, the solar system is just a dead, icy set of rocks. Not only giving life to earth but also the sun has the capability of destroying the life of the earth. Therefore, studying about mysterious properties of the sun is very important to humans.
Sunspots appear on the surface of the sun as pairs or groups due to the high magnetic field of the sun. When one of these spots is north, the polarity of the other Sunspot is south. Therefore, the magnetic field emerges through one Sunspot and goes back through another, creating an arch-shaped magnetic field loop known as prominences. Sometimes, these loops interconnect and release powerful eruptions known as solar flares. These flares eject high-energy particles toward solar systems (Mawad & Abdel-Sattar, 2020). This phenomenon is known as solar coronal mass ejections (CMEs). During a solar minimum, there will be approximately one CME for a week, but it can emit three or four CMEs for a day in during a solar maximum. Solar flares can be categorized into five classes A, B, C, M & X, according to their X-ray brightness. Powerful solar flares with higher X-ray brightness are classified in class X. Each of these classes can be divided into ten subclasses again. CMEs that emerge to surround the occurring disk of the coronagraph images are known as halo CMEs (HCMEs) (Burlaga et al., 1982). HCMEs are said to be front-sided if the eruption location of the related solar flare can be identified on the sun's visible side. Front-sided HCMEs can affect the earth more than ordinary CMEs do since HCMEs directly come toward the earth. Solar energetic particles (SEP) are highly energetic particles such as electrons, protons, and heavy-ion released by the sun due to solar flare eruptions. This phenomenon is known as a solar energetic particle event (or solar proton event (SPE) or a major proton event). The earth's magnetic field protects Earth from SEP by acting as a shield. When an HCME with a southward magnetic field hit the magnetic field of the earth, which is northward, a geomagnetic storm will appear. SPEs which are created as a result of halo CMEs are the main cause of geomagnetic storms around the earth. Studying SEP events helps to discover many details about the sun because they are made of pure solar materials.
Solar corona & CMEs can’t be observed using regular telescopes due to the low density of solar corona & high brightness of the photosphere. Coronagraph telescopes are specially designed to observe solar corona & CMEs by blocking the light of the photosphere using an obstacle. The main object of the “Solar and heliospheric observatory” (SOHO) spacecraft of NASA is to study about internal structure and dynamics of the sun, solar corona, and solar wind. Large angle spectrometric (LASCO) is the coronagraph telescope in the SOHO spacecraft. LASCO has three types of coronagraph images, namely C1, C2, and C3, which have three different visible ranges. C2 images of the LASCO telescope which has a range from 1.5 to 6 solar radii were used throughout this research. The extreme ultra-violet imaging (EIT) telescope of SOHO can get high-resolution images of the sun with five different wavelengths within the UV range. These EIT images were used to identify solar flare locations on the sun.
This research mainly focuses on developing an image processing method to study the properties of front-sided HCMEs and identify associated flare classes by analyzing coronagraph images of SOHO spacecraft from 1996 to 2019 and additional data observed by the NOAA space environment services centre.