Earth

Earth

magnetosphere

A zone of charged particles trapped by a planet's magnetic field, lying above the atmosphere.

atmosphere

Layer of gas confined close to a planet's surface by the force of gravity.

Earth

Diagram of Earth's atmosphere, showing the changes of temperature and pressure from the surface to the bottom of the ionosphere.

Earth

•Atmospheric density decreases steadily with increasing altitude

•So does pressure.

•Climbing even mountain 4 or 5 km high, clearly demonstrates the thinning of the air in the troposphere.

•i.e. Climbers must wear oxygen masks when scaling the tallest peaks on Earth.

Earth

The troposphere is the region of Earth's (or any other planet's) atmosphere where convection occurs, driven by the heat of Earth's warm surface

convection

Churning motion resulting from the constant upwelling of warm fluid and the concurrent downward flow of cooler material to take its place.

Earth

Troposphere

The Troposphere is the lowermost portion of Earth's atmosphere.

It is the densest layer of the atmosphere and contains approximately 75% of the mass of the atmosphere and almost all the water vapor

The depth of the troposphere is greatest in the tropics (about 16km) and smallest at the poles (about 8km).

Troposphere

Convection

Eventually, steady circulation patterns with rising and falling currents are established and maintained, provided that the source of heat (the Sun in the case of the atmosphere) remains intact.

Convection occurs whenever cool fluid overlies warm fluid.

Hot air rises, cools, and falls repeatedly.

Troposphere

•The troposphere is the most turbulent part of the atmosphere

•Most weather phenomena are seen here

•Usually airplanes and jets fly just above the troposphere to avoid turbulence.

Troposphere

•In the troposphere the temperature decreases with height at an average rate of 6.4 °C for every 1 km increase in height.

•This decrease in temperature is caused by adiabatic cooling

•as air rises the atmospheric pressure falls and so the air expands.

•In order to expand the air must do work on its surroundings and therefore its temperature decrease.

Stratosphere

•The stratosphere is a layer of Earth's atmosphere that is stratified in temperature, with warmer layers higher up and cooler layers farther down.

•This is in contrast to the troposphere near the Earth's surface, which is cooler higher up and warmer farther down.

Stratosphere

•The stratosphere is layered in temperature because it is heated from above by absorption of ultraviolet radiation from the Sun.

•stratosphere is situated between about 10 km and 50 km

•there is no regular convection and associated turbulence in this part of the atmosphere

Earth

Diagram of Earth's atmosphere, showing the changes of temperature and pressure from the surface to the bottom of the ionosphere.

Earth

ozone layer

Layer of the Earth's atmosphere at an altitude of 20 to 50 km where incoming ultraviolet solar radiation is absorbed by oxygen, ozone, and nitrogen in the atmosphere.

Ozone is a form of oxygen, consisting of three oxygen atoms combined into a single molecule.

The ozone layer is one of the insulating spheres that serve to shield life on Earth from the harsh radiation of outer space.

Mesosphere•The mesosphere is the layer of the Earth's atmosphere that is directly above the stratosphere and directly below the thermosphere.

•The mesosphere is located about 50-80/85km above Earth's surface.

•Within this layer, temperature decreases with increasing altitude.

•The main dynamical features in this region are the atmospheric tides which are driven by momentum propagating upwards from the lower atmosphere and extending into the lower thermosphere.

Mesosphere

•it lies between the maximum altitude for most aircraft and the minimum altitude for most spacecraft

•this region of the atmosphere has only been accessed through the use of research rockets.

Ionosphere

•The ionosphere is the part of the atmosphere that is ionized by solar radiation.

•Comprised of the Exosphere and Thermosphere

Thermosphere

•begins about 85 km above the earth.

•At these high altitudes, the residual atmospheric gases sort into strata according to molecular mass

•The few particles of gas here can reach 2,500°C (4500°F) during the day

•Even though the temperature is so high, one will not feel warm in the thermosphere.

•A thermometer would read below 0°C. This is due to the distance between the present molecules.

Exosphere

•The exosphere is the uppermost layer of the atmosphere.

•On Earth, its lower boundary at the edge of the thermosphere is estimated to be 500 km to 1000 km above the Earth's surface, and its upper boundary at about 10,000 km.

•The atmosphere in this layer is sufficiently rarefied for satellites to orbit the Earth

Exosphere

•It is only from the exosphere that atmospheric gases, atoms, and molecules can escape into outer space.

•The main gases within the exosphere are the lightest gases, mainly hydrogen and helium, with some atomic oxygen near the exobase.

Exosphere

Exobase, also called the critical level, the lowest altitude of the exosphere, is defined in one of two ways:

1.The height above which there are negligible atmospheric collisions between the particles and

2.The height above which the constituent atoms are on purely ballistic trajectories.

Magnetosphere

A magnetosphere is the region around an astronomical object in which phenomena are dominated or organized by its magnetic field.

Earth is surrounded by a magnetosphere, as are the magnetized planets Jupiter, Saturn, Uranus and Neptune.

Magnetosphere

In the magnetosphere, a mix of free ions and electrons is held mainly by magnetic and electric forces that are much stronger than gravity and collisions are rare.

In spite of its name, the magnetosphere is non-spherical.

The boundary of the magnetosphere ("magnetopause") is roughly bullet shaped, about 15 earth radius by side of Earth and on the night side (“tail”) approaching a cylinder with a radius 20-25 RE

Magnetosphere

Earth's magnetic field resembles that of an enormous bar magnet situated inside our planet. The arrows on the field lines indicate the direction in which a compass needle would point.

N

S

Magnetosphere

The north and south magnetic poles, where the magnetic field lines intersect Earth's surface vertically, are roughly aligned with Earth's spin axis.

Neither pole is fixed relative to our planet, however—both drift at a rate of some 10 km per year—nor are the poles symmetrically placed.

At present, Earth's magnetic north pole lies in northern Canada, at a latitude of about 80° N, almost due north of the center of North America

The magnetic south pole lies at a latitude of about 60° S, just off the coast of Antarctica south of Adelaide, Australia.

Magnetosphere

Two factors determine the structure and behavior of the magnetosphere:

(1) The internal field of the Earth

(2) The solar wind.

Magnetosphere

Magnetosphere

Van Allen belts

At least two doughnut-shaped regions of magnetically trapped charged particles high above Earth's atmosphere

Magnetosphere

The particles that make up the Van Allen belts originate in the solar wind.

Traveling through space, neutral particles and electromagnetic radiation are unaffected by Earth's magnetism.

Electrically charged particles are strongly influenced.

Magnetosphere

High above Earth's atmosphere, the magnetosphere (lightly shaded blue area) contains at least two doughnut-shaped regions (heavily shaded violet areas) of magnetically trapped charged particles. These are the Van Allen belts

Magnetosphere

Electrically charged particles are strongly influenced.

In this way, charged particles—i.e. electrons and protons—from the solar wind can become trapped by Earth's magnetism.

Earth's magnetic field exerts electromagnetic control over these particles, herding them into the Van Allen belts.

The outer belt contains mostly electrons; the much heavier protons accumulate in the inner belt.

Magnetosphere

A charged particle in a magnetic field spirals around the field lines. Thus, charged particles tend to become "trapped" by strong magnetic fields.

Magnetosphere

We could never survive unprotected in the Van Allen belts.

Much of the magnetosphere is subject to intense bombardment by large numbers of high-velocity, and potentially very harmful, charged particles

Particles from the Van Allen belts often escape from the magnetosphere near Earth's north and south magnetic poles, where the field lines intersect the atmosphere.

Their collisions with air molecules create a spectacular light show called an aurora

Magnetosphere

(a) A colorful aurora rapidly flashes across the sky like huge wind-blown curtains glowing in the dark. The aurora is created by the emission of light radiation after magnetospheric particles collide with atmospheric molecules. The colors are produced as excited atoms and molecules return to their ground states.

(b) The aurora high above Earth, as photographed from a space shuttle (visible at left).

Magnetosphere

On the sunlit (daytime) side of Earth, the magnetosphere is compressed by the flow of high-energy particles in the solar wind.

The boundary between the magnetosphere and this flow is known as the magnetopause. It is found at about 10 Earth radii from our planet.

On the side opposite the Sun, the field lines are extended away from Earth, with a long tail often reaching beyond the orbit of the Moon.

Magnetosphere

Earth's real magnetosphere is actually greatly distorted by the solar wind, with a long tail extending from the nighttime side of Earth well into space.

Earth’s Surface

plate tectonics

The motions of regions of Earth's crust, which drift with respect to one another. Also known as continental drift.

Earth’s Surface

Red dots represent active sites where major volcanoes or earthquakes have occurred in the twentieth century. Taken together, the sites outline vast "plates" that drift around on the surface of our planet. The arrows show the general directions of the plate motions.

Earth’s SurfaceTaken together, the plates make up Earth's lithosphere,

which contains both the crust and a small part of the upper mantle.

lithosphere Earth's crust and a small portion of the upper mantle that make up Earth's plates. This layer of the Earth undergoes tectonic activity.

The semisolid part of the mantle over which the lithosphere slides is known as the asthenosphere

asthenosphere Layer of Earth's interior, just below the lithosphere, over which the surface plates slide.

Earth’s Surface

The outer layers of Earth's interior. The rocky lithosphere comprises both the crust and part of Earth's upper mantle. It is typically between 50 and 100 km thick. Below it lies the asthenosphere, a relatively soft part of the mantle over which the lithosphere slips.

midocean ridges

Samples of ocean floor retrieved by oceanographic vessels are youngest close to the Mid-Atlantic Ridge and progressively older farther away.

Earth’s Surface

• Studies of the Mid-Atlantic Ridge have yielded important information about Earth's magnetic field.

• As hot mantle material (carrying traces of iron) emerges from cracks in the oceanic ridges and solidifies, it becomes slightly magnetized, retaining an imprint of Earth's magnetic field at the time of cooling.

• Thus, the ocean floor has preserved within it a record of Earth's magnetism during past times, rather like a tape recording.

Earth’s Surface

Samples of rock retrieved from the ocean floor often show Earth's magnetism to have been oriented oppositely from the current north—south magnetic field. This simplified diagram shows the ages of some of the regions in the vicinity of the Mid-Atlantic Ridge (see Figure 7.14), together with the direction of the fossil magnetic field. The colored areas have the current orientation; they are separated by regions of reversed magnetic polarity.