Abstract
Geomagnetic storms are initiated by organized magnetic structures of the solar wind. The intensity of magnetic storms is determined by the product of the southward component of the magnetic field and the time interval, during which the structure is located near Earth: the larger the product, the higher the storm intensity. To determine the local properties of the structures, direct spacecraft measurements of the plasma and magnetic field characteristics are used. Global properties of the structures are also of great interest. Such information can be obtained using measurements of cosmic rays by the worldwide network of neutron monitors. Magnetic clouds are examples of these structures. About 30% of magnetic storms are caused by magnetic clouds. In our theory of the formation of Forbush decrease in a magnetic cloud, it has been found that the components of the vector anisotropy in time are determined by the magnetic cloud type. Thus, using the cosmic ray method, it is possible to determine a connection between the magnetic cloud type and the intensity of the magnetic storm. Similar connections can be made for other magnetic structures.
Highlights
Interplanetary coronal mass ejections (ICMEs) strongly influence the properties of the solar wind plasma, geomagnetic activity, and the space distribution of cosmic rays (CRs)
A statistical study by Richarson and Cane [12] showed that 80% of over 300 ICMEs were accompanied by Forbush decreases (FDs)
This article presents the calculation results of the FD characteristics in an Magnetic clouds (MCs) based on the new theory, which can be used to determine a MC type using ground-based CR measurements
Summary
Interplanetary coronal mass ejections (ICMEs) strongly influence the properties of the solar wind plasma, geomagnetic activity, and the space distribution of cosmic rays (CRs). To determine the MC properties, the results of direct spacecraft measurements are mainly used [8, 9]. Due to their high mobility, CRs contain information about global properties of MCs and may provide information that cannot be locally measured [10, 11]. FDs can be useful for identifying ICMEs when limited magnetic field and plasma measurements are available. It was found that the time behaviour of the vector anisotropy components depends on the magnetic field polarization in the MC [14]. It confirms the possibility of determining the MC properties by ground-based CR measurements. This article presents the calculation results of the FD characteristics in an MC based on the new theory, which can be used to determine a MC type using ground-based CR measurements
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