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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.
The Gauss–Matuyama Reversal was a geologic event approximately 2.58 Ma when the Earth's magnetic field underwent a geomagnetic reversal from normal polarity (Gauss Chron) to reverse polarity (Matuyama Chron).
The polarity of the Earth's magnetic field is recorded in igneous rocks, and reversals of the field are thus detectable as "stripes" centered on mid-ocean ridges where the sea floor is spreading, while the stability of the geomagnetic poles between reversals has allowed paleomagnetism to track the past motion of continents.
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).
In a circularly polarized electromagnetic wave, the individual electric field vectors, as well as their combined vector, have a constant magnitude, and with changing phase angle. Given that this is a plane wave , each vector represents the magnitude and direction of the electric field for an entire plane that is perpendicular to the optical axis.
An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of wire wound into a coil. A current through the wire creates a magnetic field which is concentrated along the center of the coil. The magnetic field disappears when the current is turned off.
CEMF is the EMF caused by electromagnetic induction. Details ... The polarity of the voltage at every moment opposes that of the change in applied voltage, ...
Transverse waves that exhibit polarization include electromagnetic waves such as light and radio waves, gravitational waves, [6] and transverse sound waves (shear waves) in solids. An electromagnetic wave such as light consists of a coupled oscillating electric field and magnetic field which are always perpendicular to each other. Different ...