- 4336
- EARTH'S - Magnetic
Field Flips? Every so often, Earth's magnetic poles
completely flip. What causes this to happen? And how do these reversals affect
life on Earth?
-
------------------------- 4336
- EARTH'S - Magnetic
Field Flips?
-
- Earth, our rocky, watery oasis in the
cosmos is the ideal place for life to flourish for a number of reasons. We sit at just the right distance from our
home star for liquid water to exist on the planet's surface.
-
- The gravitational pull of other large
planets helps protect us from collisions with wandering meteorites. And the
planet's magnetic field encircles Earth with a protective barrier that shields
us from charged particles hurtling through space.
-
- Earth's magnetic field is generated by the
complex flow of molten metallic material in the outer core of the planet. The
flow of this material is affected both by the rotation of Earth and the
presence of a solid iron core, which results in a dipolar magnetic field where
the axis roughly aligns with the rotational axis of the planet.
-
- Hidden in the chemical composition of
ancient rocks are clues that Earth's magnetic field is a dynamic, shifting
phenomena. Cooling magma rich in iron minerals is pulled into alignment with
Earth's magnetic field, similar to how a needle is pulled to point towards
north on a compass. The study of ancient geomagnetic fields recorded in rocks
is the subject of a discipline known as "paleomagnetism."
-
- Earth's magnetic field has shifted and even
reversed in polarity many times in the geological past. Earth's magnetic field varies at very short
timescales and extremely long ones, ranging from milliseconds to millions of
years.
-
- The interaction of the magnetic field with
charged particles in space can alter it at short timescales, while
perturbations in the magnetic field at longer timescales are caused by internal
processes unfolding in the outer liquid core of the Earth.
-
- Fluctuations in the magnetic field caused
by the movement of metallic material in the outer core have brought about full
reversals of the magnetic field's polarity in Earth's past. Paleomagnetic
studies which have studied previous states of the magnetic field have shown
there are two possible states of polarity, the current 'normal' state, where
the lines of force of the field enter towards the center of the Earth in the
northern hemisphere and exit towards the outside of the Earth in the southern
hemisphere. The inverse, or 'reverse' polarity is also equally as probable and
stable.
-
- Paleomagnetic studies have shown that
polarity reversals of Earth's magnetic field are not periodic and cannot be
predicted. This is largely because of the behavior of the mechanisms that are
responsible for it.
-
- The flow of the metallic fluid, mostly
molten iron, in the outer core of the Earth is chaotic and turbulent. Polarity
reversals occur during periods of low geomagnetic field intensity, during which
the intensity of the dipolar component drastically decreases, and the structure
of the field is unstable.
-
- The transitory period of polarity reversal
appears as a geologically instantaneous, with a duration spanning up to a few
thousand years. When the magnetic field
is prone to flipping, it is in a state of reduced intensity, resulting in a
greater exposure of Earth's atmosphere to solar wind and cosmic rays in the
form of charged particles.
-
- During the “Laschamps excursion”, a recent
period of low magnetic field intensity which occurred only 41,000 years ago,
the global cosmic ray flux reaching the Earth's atmosphere was up to three
times higher than today's value.
-
- There is no significant evidence of a
correlation between mass extinctions of life on Earth and geomagnetic polarity
reversals. However, linking rates of species extinction with periods of low
magnetic field intensity is hindered by uncertainties in the known timescale of
these magnetic 'flips'.
-
- Additionally, magnetic reversals happen
frequently on geological timescales (several hundred times in the past 160
million years), while recorded mass extinction events occur every hundred
million years or so (much less frequently).
-
- In terms of human civilization, it is not
the shifting of the magnetic poles that is directly concerning, but the
resulting period of reduced geomagnetic field intensity. Society is growing
increasingly reliant on technology, and the effects of a reduced magnetic field
intensity should be seriously considered.
-
- In this configuration there would be a
notable increase in the penetration of charged particles into the magnetosphere
at altitudes closer to the Earth's surface, with important repercussions on our
technological world.
-
- The risks to which our planet and
civilization is exposed could have significant impacts on civil society, how we
do commerce, security, communications, power infrastructure, satellites and the
lives of people in low Earth orbit. Unfortunately, the sporadic nature of
magnetic variations and reversals means we cannot predict when exactly this
will happen, all we know is that it will happen.
-
-
February 2, 2023 EARTH'S -
Magnetic Field Flips? 4312
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------ “Jim Detrick” -----------
--------------------- --- Friday, February 2,
2024
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