Transcript magnetosphere

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
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.
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 nonspherical.
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
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.
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 windblown 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 highenergy 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 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.
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 MidAtlantic 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.