107

The Coupling of Atmospheric Electromagnetic Fields

 

oxygen due to photosynthesis led to a second important change for the organism. Tis increase in atmo­

spheric oxygen was infuenced by UV radiation from the sun to become ozone and form an ozone layer

around the earth. Te ozone layer shields out UV radiations, thus creating a mild global environment

in which life can survive on land.

Te earth is covered by an atmospheric layer that is divided into several layers. Up to an altitude

of about 12 km from the earth’s surface is called the troposphere, where meteorological phenomena

prevail, and where the atmospheric gains heat from the oceans and the earth, rises, expands and cools,

and then condenses into clouds and snow. Next, the altitude of about 10–50 km is called the strato­

sphere, where temperatures rise. Te stratosphere is formed from the presence of the ozone layer inside

the stratosphere, which absorbs the UV radiation in solar and superheats the atmosphere. Te space

above the stratosphere, 50–100 km, is called the mesosphere. From an altitude of about 80 km, ioniza­

tion phenomenon prevails and is called the ionosphere, where oxygen atoms absorb the sun’s UV radia­

tion and X-rays. Oxygen atoms collide with protons and electrons, resulting in ionization phenomena.

Depending on the distribution of electron density, the space below about 60–90 km is called the D layer,

called also D region. D layer is the bottom side region of the ionosphere with small electron densities.

Te space 90–160 km is called the E layer, called also E region. Tis layer has ionization maximum at

110 km. Te space 140–400 km is called the F layer, called also F region. In the ionosphere, the movement

of electrons and ions causes electric currents to fow, and diurnal variations in the geomagnetic felds are

caused by currents fowing in the tidal movement of the upper atmosphere and the action of the Earth’s

magnetic feld.

Every object emits light, which is determined by its temperature. The need to treat this light

quantitatively arose, and the ideal object, called the black body, was conceived. Based on this con­

cept, the energy spectrum of sunlight can be approximated by the energy spectrum of light emitted

by a black body at about 5,780 K. Radiation is transfer of energy by electromagnetic waves; solar

and terrestrial radiation are considered to be two types of heat in and out of the earth. The sun

provides the earth with 1.95 cal/cm² per minute from about 150 million km away, by means of a

wide range of electromagnetic waves with wavelength ranging from a few hundred nm to several

μm (the sun’s surface temperature is assumed 5,780 K). This is equivalent to a 1.36 kW/m² which is

called solar constant. In solar radiation, it has a maximum at a wavelength of about 0.475 μm. The

earth is warmed by its thermal energy and electromagnetic waves (from a few μm to several hun­

dred μm), corresponding to its temperature (255 K), emitted from the earth’s surface, sea surface,

and atmosphere into space. The radiant energy from the earth’s radiation and the incident energy

from the sun are in equilibrium, and the temperature of the earth’s surface is maintained at a con­

stant temperature suitable for the support of life. The earth’s radiation has a maximum intensity

of about 11 μm. It is also weakly absorbed by the earth’s atmosphere at 8–12 μm and reaches outside

the earth’s atmosphere. For this reason, we call the wavelength range, “atmospheric window.” On

the other hand, the carbon dioxide has a strong absorption band at the wavelength of 2.5–3 μm and

4–5 μm. The existence of this absorption band has led to the discussion of the increase in carbon

dioxide as a problem of global warming.

Te attenuation of UV light is due to absorption and scattering of ozone. Water and carbon dioxide

in atmosphere reduce the irradiance of infrared light. Visible light is also attenuated by the atmosphere.

Since the spectrum of solar radiation and the spectrum of earth radiation are almost separated afer

5 μm, sunlight up to 5 μm which is longer than visible light, is called near-infrared radiation and earth

radiation is called infrared radiation. By separating them in this way, we can avoid overlapping the clas­

sifcation of wavelengths and the classifcation of radiation sources. Solar radiation consists of optical

radiation from the UV, visible, and IRs of the electromagnetic spectrum, while earth radiation covers

the IR.

However, this sun-blessed, prehistoric environment of the earth was never an easy one for living

systems. Te reason is that there was intense radiation around the earth. Tis is eloquently illustrated

by the discovery of a natural fssion reactor at the Oklo deposit, in the Republic of Gabon, Africa,