THE CAUSES ANALYSIS OF STRONG GEOMAGNETIC STORMS IN THE DESCENDING PHASE OF THE 24TH SOLAR CYCLE

• Main Author: Khamdani, Muhamad
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/45670
• Institution: Institut Teknologi Bandung

Geomagnetic storm is a large-scale disturbance of the Earth's magnetic field that is the core as well as a representation of space weather. Based on hourly data geomagnetic parameter, there were 102 strong geomagnetic storms (Dst index ? -100 nT) - including 3 very strong geomagnetic storms - during 2015 to 2019, where the 24th solar cycle was in the declining phase. These geomagnetic storms were divided into 9 series phenomena. This research aims to determine the causes of the strong geomagnetic storms, both of solar and interplanetary sources. Also, the relationship of each cause to the strength and duration of a geomagnetic storm. The approach used in this research is analytical descriptive. A survey of eruptive phenomena on the surface of the Sun was carried out to determine the main source of geomagnetic storms. On the other hand, interplanetary sources are known through the analysis of solar wind plasma structures and interplanetary magnetic fields. The results showed that 8 of the 9 geomagnetic storm chains above were caused by CME, and the last one is caused by HSS from the coronal hole. Based on analysis of the solar wind plasma and interplanetary magnetic field structures, they are known that 6 series of geomagnetic storms were caused by a combination of sheath and MC structures. In addition, it was found that the duration of the geomagnetic storm was related to the peak speed of solar wind plasma. In the case of CME associated with solar flare, the duration of the solar flare also contributes to the duration of the geomagnetic storm. The delay time of the geomagnetic storm impact caused by CME correlates to the linear velocity of CME with correlation coefficient r = -0.94.