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ADVENTURES
IN GEOSPACE
In addition to providing light and warmth, the
Sun blows a million tons of matter into space every second.
This matter is in the form of hot electrified material - mostly electrons
and protons - in the fourth state of matter called
plasma. This steady stream of matter called the solar
wind travels through space at an average speed of 400km/s ("900,000
miles/hr) with extremes from 300 km/s ("700,000 miles/hr) to 900km/s
("2 million miles/hr). Particularly energetic events on the Sun -
sunspots,
solar flares and coronal mass ejections (CME)
- blast more particles into space. A typical
CME can carry 10 billion tons of matter into space.
This constant barrage of fast moving, charged
particles in the solar wind could be very dangerous to the Earth.
However, in the 1930's Chapman and Ferraro modeled that the Earth's
magnetic field provided a complete barrier to the plasma coming
from the Sun. In the picture below, the solar wind (green), moving
from left, is deflected by the magnetosphere (blue).
The collision of the supersonically flowing solar wind with the
magnetic field of the Earth forms a bow shock shown in red. The
interaction of the shocked solar wind and the Earth's magnetic field
forms what is known as the Magnetopause. The Magnetopause is the
barrier to the solar wind.
Although there is a barrier to the penetration of
the solar wind plasma, some of its electrical energy
does penetrate the Earth's magnetic shield. This
is enough to generate millions of amps of electric
current in the upper atmosphere, and can create occasional
magnetic storms. Very energetic events like Coronal
Mass Ejections can create spectacular auroras, damage satellites,
disrupt radios, burn out power transformers and corrode
pipelines. Obviously, the magnetosphere is not an
impermeable magnetic shield. In the 1960's James
Dungey provided a mechanism by which the solar wind
and its imbedded magnetic field couple to the Earth's
magnetosphere. This mechanism he called magnetic reconnection. Recent
satellite missions, many of which flew under the International Solar
Terrestrial Physics Program (ISTP), have gathered data that have
allowed scientists to build upon Dungey's theories. The new picture
of the solar-terrestrial interactions is more complex.
Powerful new
models have
been constructed. Four of the Solar Terrestrial Probes
(STP)
missions, Thermosphere-Ionosphere-Mesosphere-Energetics
and Dynamics (TIMED),
Magnetospheric Multiscale Mission (MMS),
Geospace Electrodynamics Connection (GEC)
and Magnetospheric Constellation (MagCON)
will gather important information about the dynamic
structure of the magnetosphere and its affect upon
the upper atmosphere of Earth. But first it is important
to know about Electricity,
Magnetism,
Electromagnetism.
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