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The Earth's magnetic field has alternated between periods of normal polarity, in which the predominant direction of the field was the same as the present direction, and reverse polarity, in which it was the opposite. These periods are called chrons. Reversal occurrences are statistically random.
Magnetization reversal by circularly polarized light is the fastest known way to reverse magnetization, and therefore to store data: magnetization reversal is induced on the femtosecond time scale - that translates to a potential of about 100 TBit/s data storage speeds.
The Earth's magnetic field is approximately four times stronger today than it was during the Gauss–Matuyama reversal. [4] The reversal is thought to have weakened the shielding that the magnetic field provides the surface Earth, resulting in more exposure to ionizing radiation generated by the early Pleistocene supernova , and leaving the ...
The following is a list of geomagnetic reversals, showing the ages of the beginning and end of each period of normal polarity (where the polarity matches the current direction). Source for the last 83 million years: Cande and Kent, 1995. [1] Ages are in million years before present (mya).
The solar magnetic field was first detected in 1908 by George Ellery Hale, when he showed observationally that sunspots had strong, bipolar magnetic fields. [1] With these observations, Hale also noted that the majority of sunspot groups within the same northern or southern solar hemisphere shared the same leading polarity and that this pattern reversed across the equator.
Computer simulation of Earth's field in a period of normal polarity between reversals. [1] The lines represent magnetic field lines, blue when the field points towards the center and yellow when away. The rotation axis of Earth is centered and vertical. The dense clusters of lines are within Earth's core. [2]
The magnetic north pole is constantly shifting relative to the axis of rotation of Earth. Magnetism is a vector and so magnetic field variation is studied by palaeodirectional measurements of magnetic declination and magnetic inclination and palaeointensity measurements. Earth's magnetic polarity reversals in last 5 million years.
The Brunhes–Matuyama reversal, named after Bernard Brunhes and Motonori Matuyama, was a geologic event, approximately 781,000 years ago, when the Earth's magnetic field last underwent reversal. [1] [2] Estimations vary as to the abruptness of the reversal.