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The Coupling of Atmospheric Electromagnetic Fields

The total field intensity in Japan is around 50 μT. Geomagnetism is believed to be caused by con­

vection movements in the liquid outer core of the earth. The huge current of hundreds of millions

to billions of amperes of conductive fluid flows through it. This is called self-excited magneto-

hydrodynamic dynamo. The geomagnetic field is described by three components: (1) total magnetic

intensity, (2) declination, and (3) inclination. There are solar, lunar, and diurnal variations of the

geomagnetic field. The diurnal variations may be pronounced during the day. Irregular pulsa­

tions and magnetic storms can be recorded in addition to these periodic variations. On the time

scale of hundreds of years, the earth magnetic dipole is decreasing and the magnetic field strength

decreased. It is believed that the inversion of the earth magnetic dipole occurs. This inversion

could cause appearance and disappearance of biological species and life. Unlike the magnetic field

which depends on the location on the earth, the electric field strength depends on the latitude to a

small extent.

Electromagnetic felds have been present throughout the evolution of life on earth. In the marine

environment, the geomagnetic feld is the dominant of electromagnetic felds. Due to Faraday’s induc­

tion law, the electric feld is induced in marine species, resulting from its moving through seawater in

the geomagnetic feld.

Te earth forms the global atmospheric electric circuit between earth surface and ionosphere as

shown in Figure 3.1 of the paper by Rycrof et al. (2012). It shows various important processes in the

global atmospheric electric circuit. Charge separation in thunderstorms creates a potential diference

between the highly conductive regions of the ionosphere and the earth’s surface. A global atmospheric

electric circuit is said to form between the negatively charged surface of earth and positively charged

surface of the ionosphere. Tis structure has a resemblance to the spherical capacitor.

On a dry winter day, we have had the experience of receiving a violent electric shock to our fngertips

when crossing a carpet, touching a metal doorknob or the body of a car, causing us to jump. We have

also heard the sound of small sparks when taking of a synthetic fber shirt. Tese are caused by static

electricity generated by friction and discharged between your fngertips and the knob or car body, or

between you and your synthetic fber shirt. Tis kind of charging phenomena can also be observed

in the open air. If the metal supported by insulating rods is placed at a hight of one meter above the

ground, and measured its electric potential ranging from several tens of volts to several hundreds of

volts can be observed on a sunny day. Te higher the potential rises above the ground surface, the

higher the value. When there are thunderclouds nearby, the potential is several times higher, ranging

from several thousand volts to several tens of thousands of volts. Tis is due to the presence of electric

felds, and positive and negative electrifed molecules and particles, or air ions, in the atmosphere,

which charge the metal plate. Tis kind of electrical phenomenon in the natural atmosphere is called

atmospheric electricity.

In the air at about 50 km, some of the gases are ionized by UV and X-ray from the sun and become

positive ions. Tese ions are stratifed in order to weigh, starting from the bottom, and each layer is

thought to have an amount of electrons equal to the total amount of positive ions.

Te higher the altitude, the stronger the UV radiation and X-rays which increase ionization and ion

density. Also, the mean free path of the ions increases because the density of air decreases. Terefore,

the electrical conductivity also increases, and there is no diference in electrical potential in the hori­

zontal direction. For example, the electrical conductivity at 1, 5, and 10 km from the surface is about 2.5,

10, 25 × 10⁻¹⁴ S/m, respectively. Te number of small ions at an altitude of 15 km is about 5,000 per cc,

producing an electrical conductivity of 100 × 10⁻¹⁴ S/m. Afer 50 km above the ground, the conductiv­

ity increases rapidly, and at 100 km it reaches about 10⁻² S/m, about the same as the conductivity of the

earth can be assumed that there is a good conductor called the ionosphere 100 km above the ground. On

a global scale, electromagnetic felds are ubiquitous, and their links to biology have been studied more

extensively over the last century (König, 1977; König et al., 1981). More recently, evidence has emerged

that biology is linked with static electric felds throughout the earth’s atmosphere (Clarke et al., 2013;

Morley and Robert, 2018; Hunting et al., 2019).