Kristian Birkeland ran expeditions to northern Norway
and established a network of observatories
to see how the magnetic field related to the northern lights.
He proposed in 1908 that Earth’s magnetic field
guided electrons ejected from the sun toward the poles
where they interacted with currents, now known as Birkeland currents,
that flow along geomagnetic field lines from the north pole.
Birkeland’s theories were ridiculed
until rockets were deployed
to permit direct measurements from space.
*
Birkeland died in 1917 but Carl Størmer
was inspired by Birkeland to study
the motion of charged particles in Earth’s magnetosphere
and develop mathematical models of them,
predicting orbits of charged particles
that were later confirmed by James Van Allen.
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James Van Allen designed the scientific instrumentation
for Explorer 1, the first satellite launched by the United States,
and the first spacecraft to detect a Van Allen radiation belt.
Van Allen’s instrumentation included
an omnidirectional Geiger-Müller tube
to detect cosmic rays
five temperature sensors
an acoustic detector and a wire grid detector
to detect impacts of cosmic dust
packed into a cone and cylinder a yard long
and six inches in diameter.
Charged particles trapped by Earth’s magnetic field
overwhelmed the Geiger counter so that it read zero
as Explorer 1 passed through the inner Van Allen belt.
Shields
The inner Van Allen belt
contains mainly high-energy electrons
trapped by earth’s magnetic field.
The outer Van Allen belt
contains high-energy electrons and ions
and fluctuates in response
to geomagnetic storms.
A transient third belt just outside the atmosphere
contains unrelativistic particles
that merge with the outer belt.
Van Allen belts protect the atmosphere
against the solar wind; however,
charged particles in the belts
cause problems for satellites.
Auroras
Winds of charged particles from the sun
batter the magnetosphere of the earth
so both rain charged particles
into the upper atmosphere at high latitudes.
which excites atmospheric gases
to emit a diffuse glow or folded curtains of light
red from atomic oxygen at high altitudes
green at lower altitudes from nitrogen
transfering energy to oxygen
blue and red from nitrogen at lower altitudes
combine for yellow and pink.
Lights in the sky
They say there are lights in the sky.
Some who say so are deluded;
others say anything to get attention.
But lights are in the sky.
There must be a good explanation.
Galileo named the northern lights Aurora Borealis in 1619.
The same phenomenon near the south pole is called Aurora Australis.
Venus, Mars, Jupiter, Saturn, Uranus, and Neptune also get auroras.
Without a molten core, Earth would have no magnetic field, no aurora,
and no atmosphere, like Mars.
Galileo named the northern lights Aurora Borealis in 1619. The same phenomenon near the south pole is called Aurora Australis. Venus, Mars, Jupiter, Saturn, Uranus, and Neptune also get auroras.
Without a molten core, Earth would have no magnetic field, no aurora, and no atmosphere, like Mars.
See also in The book of science:
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