The Earth’s Magnetic Field - Ultra and Extremely Low Frequency Electromagnetic Fields - page 3

Fig. 1.1 Sketch of the Earth interior. Taken from the site http://blog.world-mysteries.com/science/
earth-crust-displacement-and-the-british-establishment/
The presence of the molten core inside the Earth has been discovered by
Gutenberg ( 1914 ). At the mantle-core interface the velocity of longitudinal seismic
wave (P -wave) decreases abruptly from 13.6 km/s in the mantle down to 8.1 km/s
in the core, while the velocity of transverse wave (S-wave) falls off stepwise with
depth from 7.3 km/s up to zero. This means that the shear modulus inside the outer
core equals zero and hence the core is liquid. The outer core is about 30 % of the
Earth mass and the core radius is evaluated as 3,483 km. The outer core consists of
the mixture of molted sulfur (12 %) and iron (88 %). The volume of molten material
inside the core is five times as much as the Moon.
There is a solid inner core inside the outer core. The inner core is about 1.7 %
of the Earth mass and the core radius is evaluated as 1;240 ˙ 10 km. The inner
core consists of ferro-nickel-alloy (80 % Fe and 20 % Ni). Present-day estimation
of the parameters in the Earth center is as follows: the pressure is 3:6 10 11 Pa,
mass density is 12:5 10 3 kg=m 3 , and temperature is about 5:3 10 3 K, that is
close to the temperature of the Sun surface. The core conductivity is assumed to be
.7 ˙ 2/ 10 5 S=m.
According to contemporary data, the heat flow from the Earth's interior is not
only due to thermal conductivity but also due to convection of the melted material.
The heated material of the core goes up due to its decreased density. At the
boundary between the core and mantle the upgoing material transmits part of its
energy to the overlying rock followed by the material cooling. This results in the
material lowering caused by the increases of its density. Additionally, the convection
builds up as a result of light fractions floating up and heavy fractions falling off.
Consolidation of fluid around the solid inner core followed by evolving of latent
heat leads to an enhancement of the convection. It thus appears that the main source
of the movements inside the outer core is the decrease of gravitational energy that
is accompanied by the growth of the inner core. It is now unclear whether the