Why do you keep creating these ridiculous IO entries using other peoples copyrighted photo's?

This is not a kickstarter site!

The discovery that the earth has a

own magnetic field occurred in 1600 by a
scientist named William Gilbert. He reached
conclusion that the Earth behaved like a
big magnet. The study of Earth's magnetic field
(or geomagnetic) has always been of great
historical importance, both for the guidance in
navigations and for a better understanding
on planet Earth. Nowadays there is too much
research being developed on
geomagnetism. Some topics are still in
full discussion, for example, processes
This magnetic field originating and their
consequences for the Earth. This course
We discuss topics from the basic to the
more complex issues that are currently
being studied.
As the magnetic field is a quantity
Vector with intensity and direction, we can
measure it by its components (Figure 1): North
(X), east (Y), vertical (Z) and its angles
magnetic declination (D) and magnetic tilt
(I). The horizontal field component is
represented by H, and the total intensity of F (or
by B). The horizontal component (H) points to the
magnetic north. The magnetic declination is
angle between magnetic north and geographical.
The magnetic field strength is
measured in a unit called Tesla. The field
geomagnetic is expressed in nano-tesla (nT) which is
equal to 9.10 tesla. The field strength in
Earth's surface is of 70,000 nT order
near the poles and about half of this amount
near the equator (Figure 2). But there is a region
Earth where the field is weaker and this area is
called the South Atlantic Magnetic Anomaly
(AMAS). Much is located in AMAS

The magnetic field observed is the result

the contribution of different sources: the field
core, the external field and the field induced
crustal field. The core fields, and crustal
induced will be addressed in detail in module
2, since the external field will be described in Module 3.
However, for an overview of the field
geomagnetic, explained the main
Then in characteristics.

Field core (and main course): the field
generated in the magnetic core has a
about dipole geometry. this field
corresponds to about 90% of the observed field,
so the core is also called field
main. This field operates as a dipole
"Protective shield" for the particles that come from
Sun and cosmic rays propagate in
direction of our planet. The term dipole means two poles, north and
Southern, for example, a magnet. The LINES
MAGNETIC FIELD STRENGTH a magnet out
the North Pole to the South Pole.

LINES OF MAGNETIC FIELD STRENGTH
describe the structure of the magnetic field. THE
compass needle points along a
field line. The closer the
field lines, the greater the intensity of the
even (as in the Earth's magnetic poles
or a magnet). As for the outlying field lines
represent weaker magnetic fields.

However this magnet convention is not
adopted by geophysicists in the case of the Earth. note
that on our planet currently lines
force out of the geographic south to north
geographical

However, geophysicists consider the magnetic poles according to the

geographic poles. Therefore, the current configuration
magnetic field indicates that the magnetic south pole
It is close to the geographic South Pole and vice versa

This association is not permanent, since
that due to reversals of the field, the poles
reverse direction.

But you can imagine how the interior of the
Dirt? The interior of the Earth has four layers
main: the crust, the mantle, the outer core and the
inner core (Figure 5). Each layer has
Specific features of composition, pressure and
temperature.

The crust has different thicknesses in
continents and oceans: a few dozen
km on the continents and less than ten
kilometers in the oceans. Below the crust, there is
mantle that reaches a depth of
approximately 2891 km. The core
outside is the only liquid layer of the Earth and reaches
a depth of 5150 km. already
inner core is solid and extends to 6371 km
(Earth's radius).
But as we know about the existence
these layers and divisions among them? For
answer this question refer to:

However, in reality, there is a magnet in
Earth's core. What exists is fluid composed
mainly iron (Fe) and nickel (Ni) with a
ELECTRIC high conductivity (σ = 5x105
  S / m).
This fluid is constantly moving in
presence of a pre-existing magnetic field.
Consequently, the fluid induces currents
power that extend the magnetic field.

ELECTRICAL CONDUCTIVITY measures
ability of a material conducts a
electric current. It is usually represented
by the Greek letter sigma (σ) and your unit is
Siemens / meter (S / m). Metals, e.g.
They have a high electrical conductivity and
they are called conductors. A few of
Examples of electrical conductivity
materials are below (for a
temperature 20 ° C):

External: field is generated by SOLAR WIND to
magnetosphere reaching the earth, which is the region in
around the Earth where the magnetic field is
confined. Part of the magnetosphere facing for
Sun is compressed by the solar wind reaches 10 Rays
Earth (Re = 6371km). Already the opposite of the Sun, is
elongated and is called the magnetotail,
Re reaching 60 (Figure 6). Another region where the
the outfield is produced is called
ionosphere and extends 60 km to 1500 km. THE
ionosphere is divided into layers with thicknesses and
different ionization.

O VENTO SOLAR é composto por partículas
energizadas e ionizadas, basicamente elétrons
e prótons que fluem do Sol para todas as
direções. O vento solar é originado na camada
mais externa do Sol, chamada corona. A sua
velocidade é de aproximadamente 400 km/s,
mas pode chegar até 800 km/s.

Crustal: field is generated by magmatic rocks
that exist in the outermost layer of the Earth. THE
first observation of the existence of the field
Earth's magnetic occurred due to property
to attract a magnetic rock, the natural magnet.
The ancient magnetic field is recorded by rock

containing magnetic minerals. These minerals
They act as small magnets and are oriented to
According to the natural magnetic field that
time when the rocks were formed. This type
magnetization is called permanent.
When we measure the magnetic field
a particular location, the influence of all
sources is contained in the registry.

There is no
automatically to separate the core field
the outfield at the moment we are
making measurements. This is done later
using mathematical methods

The first field observations
geomagnetic shown that the magnetic field
Earth is not static, but changes over time
a wide time scale: from milliseconds to
millions of years. Figure 8 shows a record of
magnetic declination in China in the year 720 to
1829.
Generally speaking, we can divide the variation
Thunderstorm geomagnetic field on two tracks:
the longest variations of millions of years
decades, are generated by the core and
shorter period changes, such as magnetic storms are generated by the field

external.Are the magnetic rocks that record the

paleomagnéticas variations in scale of millions
years. A well known fact is that the field
Magnetic reversed its polarity many times in
geological time. At present, the magnetic dipole
points of the southern hemisphere to the northern hemisphere
(see Figure 4), but in the past this direction has already been
reversed many times.
As for the changes in the magnetic field
hundreds of years are called scale
secular variation. Since the beginning of the observations
continuing the geomagnetic field, to about 170
years ago, the intensity of the magnetic field
overall is decreasing at a rate of 6% in 100
years. However, the decrease of the intensity of
field is not equal in all regions of the globe;
especially in the AMAS region this decrease
It is occurring faster. Other
interesting feature of secular variation is the
shift from the countryside to the west. Watch the video
BfS.mov and note that the AMAS was in Africa for
around 1600 and moved in the direction of
Brazil, where he currently finds himself.
There are other temporal variations more
short due to solar activity, ranging from tens
years to milliseconds. For example, there variations in the course of 1 day (called variation

daytime). When solar activity is not very
active, the day is called "Day geomagnetic
calm "or Sq (English:" Solar-quiet "). But when the
solar activity is very active, occur
magnetic storms that last for hours.
During magnetic storms, can
experience problems in satellites systems
navigation and radio-communication. these disorders
occur more frequently in areas where the
field strength is weaker (AMAS), or
where the "protective shield" of the earth (field
principal) is weaker.

 Figure 1: Modified book "The Magnetic Field

of the Earth- paleomagnetism, the core, and the
deep mantle "Merrill, R. T. et. al. (1996)
Figure 3: NASA homepage on fields
magnetic "Magnetic Fields"
http://helios.gsfc.nasa.gov/magfield.html
Figure 4: Homepage of the European Space Agency.
Author: Peter Reid (2003)
http://sci.esa.int/sciencee/www/object/index.cfm?fobjectid=41209

Figure 5: Homepage on Earth layers
"Into the dephts of the Earth"
http://sprg.ssl.berkeley.edu/~ateste/AlexandraTest
and / Earth_layers.html
Figure 6: NASA Homepage
http://sohowww.nascom.nasa.gov/gallery/images/
magfield.html
Figure 7: Scientific Article
N. Olsen G. Hulot · · Sabaka T. J. (2010).
Figure 8: Homepage on paleomagnetism
Author: Lisa Tauxe
http://magician.ucsd.edu/essentials/WebBookch14
.html # WebBookse89.html