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This graph shows the flux of particles seen
near Earth. It covers an extremely wide range
of particle energies. This is an "integral"
distribution, that is, it shows the flux
of particles with energies above the energy
shown on the horizontal axis. Note that only
those particles at the higher end of the
energy scale (towards the right hand side)
can penetrate the aluminum skin of a spacecraft
which is typically around 1 gm/cm2. |
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Galactic Cosmic Rays are composed of many
elements but the lighter nucleii dominate.
Note that the vertical axes are logarithmic.
For example, in the right graph, the hydrogen
(H) peak is about 10 times higher then the
helium (He) peak and almost 10,000 times
higher than the iron (Fe) peak. |
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Both Galactic Cosmic Rays and the solar wind
contribute particles to the Earth's radiation
belts (although GCR is thought to be the
predominate source). Because the Earth's
magnetic field is not symmetric, there is
a "hot spot" above the east coast
of Brazil called the South Atlantic Anomaly.
This graph shows the energy distribution
of the protons which are a primary component
of the radiation in the SAA. |
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Energetic particles from the sun, mostly
protons and helium nucleii, present
a significant
danger to men and equipment during
solar
storm activity. This graph shows the
energy
distribution of protons arriving in
Low Earth
Orbit during various solar storms,
identified
by their date. The curves indicate
the flux
of particles with energies above the
energy
shown on the horizontal axis (integral
distribution).
For example, the 1972 event produced
over
10000 protons/cm2/sec/sr with energies
above
10MeV. |
