Sponge: List the six layers of the Earth.

Atmosphere

A mixture of gases:N2 78%O2 21%Ar 0.9%CO2 0.03%

Water vapor in the atmosphere varies from 0.1% to 3%.

What makes Earth unique is Oxygen.

The presence of water and carbon dioxide is also important.

The atmosphere provides oxygen, protects the Earth from harsh solar and cosmic radiation, keeps most meteoroids from becoming meteorites, and keeps the Earth’s surface warm.

The atmosphere is like a protective blanket for the Earth.

The atmosphere is relatively small, half below 5 km, 99% below 30 km.

Density and pressure decrease steadily with height.

Layers of atmosphere:

Troposphere - below 15 kmStratosphere - 15 to 40-50 kmMesosphere - 50 to 90 kmThermosphere - above 90 kmExosphere - above 250 km

The troposphere is the area where convection occurs.

This rising of warm air and sinking of cooler air is powered by the surface heat of the Earth.

These convection currents are responsible for all the weather on Earth.

Temperature decreases with altitude in the troposphere.

The top of the troposphere is the tropopause. Above this, in the stratosphere, the air is still.

Within the stratosphere, the ozone layer is found.

In the ozone layer the temperature increases as solar UV radiation is absorbed by O2, O3 (ozone), and N2.

This absorption of UV radiation protects the Earth from its effects.

The ozone layer stretches into the mesosphere, although the term “stratosphere” is often used to refer to both the stratosphere and the mesosphere.

In the thermosphere, the temperature increases with altitude because the high-energy part of the Sun’s spectrum splits molecules into atoms and atoms into ions.

This ionization of the atmosphere is significant above about 100 km. This electrically conductive part of the atmosphere is called the ionosphere.

This ionosphere is part of the thermosphere and can actually reflect certain radio wavelengths. (AM)

The surface of the Earth absorbs much energy from the Sun and reradiates it. Most of this energy escapes into space, but infrared radiation is partially blocked by the carbon dioxide and water vapor in the atmosphere.

This partial blocking of solar radiation is called the greenhouse effect.

Warmed air rises and is replaced by air that has been cooled in the upper atmosphere. This produces a circulation pattern called a convection cell.

This rising and falling air affects atmospheric heating and also produces surface winds. Passenger aircraft tend to fly above these disturbances, in the lower stratosphere.

The magnetosphere is the region around the Earth influenced by the Earth’s magnetic field. This field is similar to that of a bar magnet roughly aligned with the spin axis of the Earth.

It was detected by satellites launched in the late 1950’s. It contains two doughnut-shaped zones of high energy particles (one about 3000 and the other 20 000 km above the Earth’s surface), called the Van Allen Belts. The radiation here is lethal.

The magnetic field is believed to be caused by rotating, conducting material (molten iron and nickel) flowing in the Earth’s outer core. This is called dynamo theory.

The high energy particles in the Van Allen Belts are collected from the solar wind and are trapped because they are charged particles (primarily protons and electrons).

These charged particles often escape near the poles, where the magnetic field intersects the atmosphere. They rip apart air particles, creating spectacular lights called the aurora.

In the north, these lights are called the aurora borealis (northern lights). In the south, they are called the aurora australis (southern lights).

Aurorae as seen from ISS

Perseid meteor to the left

The Aurora Australis (from space)

Earth isn’t the only planet to have aurorae. The next three pictures are of aurorae on Saturn. Notice the strange hexagonal shape on the last image.

The magnetic field is distorted by the solar wind. On the daytime side of the Earth, the magnetosphere is compressed.

The boundary between the magnetosphere and the solar wind is called the magnetopause and is found about 10 Earth radii from the Earth’s surface.

On the side opposite the Sun, the field lines are extended, often reaching beyond the Moon’s orbit. As a result the magnetosphere is “teardrop”-shaped.

The magnetosphere screens out much destructive radiation from the solar winds.

In the year 2000, we were at the peak of solar activity and the highest solar winds. If you fly 75,000 air miles on passenger jets, it is like being exposed to 20 X-ray procedures.