Earth Orientation
Earth's magnetic field
Earth's magnetic field is approximately a magnetic dipole, with
the magnetic field S pole near the Earth's geographic north pole
and the other magnetic field N pole near the Earth's geographic
south pole. This makes the compass usable for navigation. The cause
of the field can be explained by dynamo theory. Magnetic field
extends infinitely, though it weakens with distance from its
source. The Earth's magnetic field, also called the geomagnetic
field, which effectively extends several tens of thousands of
kilometres into space, forms the Earth's magnetosphere. A
paleomagnetic study of Australian red dacite and pillow basalt has
estimated the magnetic field to be at least 3.5 billion years
old
South Pole
The South Pole, also known as the Geographic South Pole or
Terrestrial South Pole, is one of the two points where the Earth's
axis of rotation intersects its surface. It is the southernmost
point on the surface of the Earth and lies on the opposite side of
the Earth from the North Pole. Situated on the continent of
Antarctica, it is the site of the United States Amundsen-Scott
South Pole Station, which was established in 1956 and has been
permanently staffed since that year. The Geographic South Pole
should not be confused with the South Magnetic Pole.
Magnetic Field Generator
The Earth's magnetic field is generated within its molten iron
core through a combination of thermal movement, the Earth's daily
rotation, and electrical forces within the core. These elements
form a dynamo that sustains a magnetic field that is similar to
that of a bar magnet slightly inclined to a line that joins the
North and South Geographic Poles. A compass placed in this magnetic
field thus does not point due north, declination measures the angle
between the compass reading at any point on the Earth's surface and
true north (measured in degrees). The geomagnetic reference model
is the basis for establishing the declination and its variation
across the surface of the globe.
Influence of the Sun
Electrical particles streaming from the sun cause the "solar
wind" which warps Earth's geomagnetic field lines, flattening them
on the sun-ward side and stretching them out on the downstream
side. The influence of this distortion of the geomagnetic field is
quite small near Earth's surface (except during solar eruptions
associated with sunspots) and becomes larger with increasing
distance from Earth.
Importance
The South Pole, also known as the Geographic South Pole or
Terrestrial South Pole, is one of the two points where the Earth's
axis of rotation intersects its surface. It is the southernmost
point on the surface of the Earth and lies on the opposite side of
the Earth from the North Pole. Situated on the continent of
Antarctica, it is the site of the United States Amundsen-Scott
South Pole Station, which was established in 1956 and has been
permanently staffed since that year. The Geographic South Pole
should not be confused with the South Magnetic Pole.Earth is
largely protected from the solar wind, a stream of energetic
charged particles emanating from the Sun, by its magnetic field,
which deflects most of the charged particles. Some of the charged
particles from the solar wind are trapped in the Van Allen
radiation belt. A smaller number of particles from the solar wind
manage to travel, as though on an electromagnetic energy
transmission line, to the Earth's upper atmosphere and ionosphere
in the auroral zones. The only time the solar wind is observable on
the Earth is when it is strong enough to produce phenomena such as
the aurora and geomagnetic storms. Bright auroras strongly heat the
ionosphere, causing its plasma to expand into the magnetosphere,
increasing the size of the plasma geosphere, and causing escape of
atmospheric matter into the solar wind. Geomagnetic storms result
when the pressure of plasmas contained inside the magnetosphere is
sufficiently large to inflate and thereby distort the geomagnetic
field. The solar wind is responsible for the overall shape of
Earth's magnetosphere, and fluctuations in its speed, density,
direction, and entrained magnetic field strongly affect Earth's
local space environment. For example, the levels of ionizing
radiation and radio interference can vary by factors of hundreds to
thousands; and the shape and location of the magnetopause and bow
shock wave upstream of it can change by several Earth radii,
exposing geosynchronous satellites to the direct solar wind. These
phenomena are collectively called space weather. The mechanism of
atmospheric stripping is caused by gas being caught in bubbles of
magnetic field, which are ripped off by solar winds. Variations in
the magnetic field strength have been correlated to rainfall
variation within the tropics.
The Earthcache
To claim this Earthcache you must go near the published
coordenates and send to me the answers for the following questions
after visiting the published coordinates:
1. What happens to your compass?
2. What is written in the mark?
3. Why does the Magnetic South Pole change from time to
time?
You may take a picture of you and the South Pole Marker, be
creative After you receive my mail validating your answers you may
put it in your log.