Analysis of Slow Partial Halo CME Events with Velocity of 100-200 km/s: An Observation through CALLISTO System

Abstract

Halo event of coronal mass ejections (CMEs) had been once in a while reported in coronagraph observations of the Sun before the Solar and Heliospheric Observatory (SOHO) mission has been carried out. However, since mid-1996 the SOHO Large Angle Spectrometric Coronagraph (LASCO) instruments have observed numerous halo or partial-halo CMEs. Partial halo is when CMEs aimed at Earth which is called as "halo events" because of the way they look in coronagraph images. As the expanding cloud of an Earth-directed CME becomes larger and it appears to envelop the Sun, forming a halo around our star. Statistical interpretation states that most of the halos CMEs occur at average speed of ~957 km/s. In 2015, eight (8) halo CMEs events were detected accompanied by slow partial halo CMEs. Sunspot number, solar radio flux and solar wind involves in interpreting the slow movements of halo CMEs. In this paper, we study partial halo CME events with slow velocity and we discussed the slow partial halo CMEs which is due to the weak magnetic fields affect from low solar radio flux and solar wind fluctuation. The slow halo CME events were observed through CALLISTO System and compare it with database from CACTUS. As a result, we found that there are slow halo CMEs occur with velocity as low as 100- 200km/s.