Abstraction
Earth’s magnetic field shields life on Earth from the harmful solar wind. However, its origin is not well understood.
The dynamo theory is usually employed to explain the origin. However, it cannot account for the magnetic fields on other planets, especially those with cooled cores.
In light of new understandings of superconductivity, a new hypothesis is proposed in this study to provide a general mechanism for the origin of planetary magnetic fields.
The “unified theory of low and high-temperature superconductivity” suggests that superconductors are the ordinary state of matter and are common at high pressures. As pressure increases deep into Earth, superconducting substances likely exist under the mantle. Driven by the rotation of Earth, the floating superconductors on the outer core accumulate towards the equator and eventually assemble into a belt looping around the core under the equator, producing a resistance-free path for currents. Earth's magnetic field was created by a Mesnner-like effect in the Sun’s magnetic field. The field compensates Sun’s field inside and superimposes it outside of Earth. Without electrical resistance in the superconductor belt, currents loop indefinitely under the equator, maintaining the geomagnetic field.
Convections in the outer core disturb the loop and occasionally break its continuity, causing polar wandering and paleomagnetism discontinuity. As the loop resamples each time, the polarity of the new field may be created in a different direction depending on whether the north or south pole is tilted towards the Sun at different seasons, resulting in a magnetic reversal. Superconductors may also be responsible for the magnetic origin of other planets. As planets cooled down, the superconductors froze inside the planets. Some might survive various celestial events throughout the planet's history, even with significant orbital changes, which explains the large angle and offset between the magnetic dipole and rotation axis of both Uranus and Neptune. Introduction Earth’s magnetic field extends from Earth’s interior out several tens of thousands of kilometers into space above the ionosphere, known as the magnetosphere. The magnitude of Earth’s magnetic field at the surface ranges from 0.25 to 0.65 G. [1] The intensity of the magnetic field changes over time. Over the last two centuries, the strength has decreased at a rate of 6.3% per century. Without the magnetic field, the charged particles from solar wind and cosmic rays would reach the surface and kill the lift on Earth. Charged particles moving in the magnetic field are deflected by the Lorentz force, spiral along magnetic lines, and converge at the north or south pole. Radiation is released as positive and negative charges merge. Photons are also emitted when high-energy particles collide with air molecules. Polar lights are caused by the particles before reaching the surface of the Earth, such as in Figure 1. This is why auroras are often seen in the sky at high latitudes.
The Earth’s magnetic field may be represented by a magnetic dipole through the center of Earth currently tilted at an angle of about 11 o with respect to the axis of Earth's rotation. While the north and south magnetic poles are usually located near the geographic poles, they move slowly and continuously over geological time scales, namely polar wandering. Occasionally, Earth’s magnetic poles may trade places, known as magnetic reversals. The magnetic field has alternated between periods of normal polarity, in which the predominant direction of the field is the same as the present, and reverse polarity, in which it is the opposite.
The Earth’s magnetic field may be represented by a magnetic dipole through the center of Earth currently tilted at an angle of about 11 o with respect to the axis of Earth's rotation. While the north and south magnetic poles are usually located near the geographic poles, they move slowly and continuously over geological time scales, namely polar wandering. Occasionally, Earth’s magnetic poles may trade places, known as magnetic reversals. The magnetic field has alternated between periods of normal polarity, in which the predominant direction of the field is the same as the present, and reverse polarity, in which it is the opposite.
Earth’s magnetic reversal history has been well preserved on the seafloor as the ocean floor spreads from the mid-ocean ridge, Figure 2.
[2] The direction of the magnetic field was frozen in
the new ocean floor that was just formed in the mid-ocean ridge. Like a tape recorder, the ocean floors recorded the change history of the Earth’s magnetic field. By studying paleomagnetism, scientists were able to reconstruct magnetic reversal history.
[3] Reversal occurrences are statistically random, lasting as little as 200 years. The latest brief reversal happened 41,000 years ago and lasted only about 440 years.
There have been 183 reversals over the last 83 million years.
Post continues at: https://www-cs.stanford.edu/people/zjl/pdf/geof8.pdf
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