Earth

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

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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.
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Earth
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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).
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Troposphere
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Convection
Convection occurs whenever cool fluid overlies
warm fluid. Hot air rises, cools, and falls
repeatedly.
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.
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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.

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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.

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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.

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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

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

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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.

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Ionosphere

• The ionosphere is the part of the atmosphere that
  is ionized by solar radiation.
• Comprised of the Exosphere and Thermosphere

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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 2,500C
  (4500F) during the day
• Even though the temperature is so high, one will
  not feel warm in the thermosphere.
• A thermometer would read below 0C. This is due
  to the distance between the present molecules.

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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

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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.

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Exosphere

• Exobase, also called the critical level, the
  lowest altitude of the exosphere, is defined in
  one of two ways
• The height above which there are negligible
  atmospheric collisions between the particles and
• The height above which the constituent atoms are
  on purely ballistic trajectories.

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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.
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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
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Magnetosphere
N
S
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.
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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, howeverboth drift at a rate of some 10
km per yearnor 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.
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Magnetosphere

• Two factors determine the structure and behavior
  of the magnetosphere
• The internal field of the Earth
• The solar wind.

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Magnetosphere
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Magnetosphere
Van Allen belts At least two doughnut-shaped
regions of magnetically trapped charged particles
high above Earth's atmosphere
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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.
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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
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Magnetosphere
Electrically charged particles are strongly
influenced. In this way, charged particlesi.e.
electrons and protonsfrom 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.
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Magnetosphere
A charged particle in a magnetic field spirals
around the field lines. Thus, charged particles
tend to become "trapped" by strong magnetic
fields.
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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
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Magnetosphere

• 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).

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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.
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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.
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Earths Surface
plate tectonics The motions of regions of
Earth's crust, which drift with respect to one
another. Also known as continental drift.
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Earths 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.
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Earths Surface
Taken 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.
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Earths 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.
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midocean ridges
Samples of ocean floor retrieved by oceanographic
vessels are youngest close to the Mid-Atlantic
Ridge and progressively older farther away.
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Earths 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.

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Earths Surface
Samples of rock retrieved from the ocean floor
often show Earth's magnetism to have been
oriented oppositely from the current northsouth
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.