Document Details

Document Type : Thesis 
Document Title :
Study of Transient Modulation of Galactic Cosmic Rays Caused by Solar Eruptions and Related Interplanetary Structures
دراسة التعديل العابر للأشعة الكونية المجرية الناتج عن الانفجارات الشمسية والهياكل البين كوكبية ذات الصلة
 
Subject : Faculty of Science 
Document Language : Arabic 
Abstract : We have studied the transient modulation of galactic cosmic ray intensity in the interplanetary space. The large-amplitude transient decreases (Forbush decreases) are mainly caused by coronal mass ejections (CMEs), particularly when the CME is associated with shock in interplanetary space. At the Earth, the neutron monitors have detected such decreases in cosmic ray intensity. We have studied these decreases detected during two solar cycles 23 and 24 (1995-2017). As geomagnetic storms are also caused mainly by CMEs, we have studied certain properties of these geomagnetic disturbances also during the time of Forbush decreases. During the passage of CMEs and associated shock structures, solar wind plasma and field parameters (solar wind velocity, interplanetary magnetic field strength (IMF) and its north-south component etc.) vary significantly. The amplitudes and variations in these parameters have been suggested to be related to amplitudes of Forbush decreases/geomagnetic storms. However, not all these interplanetary plasma and filed parameters are equally important in producing Forbush decreases or geomagnetic storms. In order to search for the relative importance of various interplanetary plasma and magnetic field parameters in producing Forbush decreases, we have analyzed some selected interplanetary plasma and field parameters (solar wind velocity, IMF and its north-south component) during the Forbush decreases. These decreases have two main parts (decrease and recovery part). Thus, not only the amplitude decreases but also the recovery characteristics of Forbush decreases have also been studied in this work. After study of the relationship between amplitude of Forbush decease and peak value of three plasma/field parameters, we found that the speed of CME in interplanetary space is best related with the amplitude of cosmic ray decrease. However, the southward component of the IMF is of significant importance in generating the geomagnetic disturbance during the passage of interplanetary CMEs and their associated structures. It is generally believed that recovery of the Forbush decreases is exponential in nature. However, our analysis of recovery characteristics of selected decreases shows that some of them recover linearly instead of exponentially. 
Supervisor : Prof.Dr. Badruddin Zaheer Ahmad 
Thesis Type : Master Thesis 
Publishing Year : 1441 AH
2020 AD 
Co-Supervisor : Dr. Aied Al-ruhaili 
Added Date : Tuesday, May 19, 2020 

Researchers

Researcher Name (Arabic)Researcher Name (English)Researcher TypeDr GradeEmail
رنيم فيصل الغامديAl-ghamdi, Raneem FaisalResearcherMaster 

Files

File NameTypeDescription
 46120.pdf pdf 

Back To Researches Page