The Earth’s Magnetic Field - Ultra and Extremely Low Frequency Electromagnetic Fields - page 2

Chapter 1
The Earth's Magnetic Field

Abstract This chapter deals with the basics of the Earth's magnetic field.
Hydromagnetic dynamo operating in the Earth's fluid outer core is treated as a
main source of the Earth's magnetic field. Here we discuss the interaction between
solar wind and the Earth's magnetosphere that forms the global magnetospheric
configuration as well as the impacts of the magnetic storms on the Earth
environment and space weather. Basics of Magnetohydrodynamic (MHD) waves in
the magnetosphere/ionosphere are studied.

Keywords Hydromagnetic dynamo ￿ Magnetic storm ￿ Magnetosphere

￿ Magnetohydrodynamic (MHD) waves ￿ Solar wind

1.1 Origin of the Earth's Magnetic Field

1.1.1 The Earth's Interior Structure

In this section we deal first with an overview of the origin of the Earth's magnetic
field. We start with a brief study of the internal construction of the Earth since
a source of the geomagnetic field is contained (hidden) inside the Earth's core.
According to modern seismic data, the Earth's interior can be split into three basic
classes: solid crust, mantle and core which is in turn divided into outer core and
inner core, as illustrated in Fig. 1.1 (Jeffreys 1970 ;Bott 1982 ; Zharkov 1983 ;Brown
and Mussett 1993 ). The Earth's crust forms continents and oceanic basement. The
effective depth of the crust is about 35 km. The crust is divided from the rocks of
dense mantle with a sharp seismic boundary, which has been termed Mohorovicic
boundary (e.g., see the topic by Nikolaevskiy 1996 ). The velocities of longitudinal
and transverse seismic waves enhance sharply at this boundary. The silicate cover
or the Earth mantle lies in the range of depths 35-2885 km.