magnetic reversal


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magnetic reversal

[mag′ned·ik ri′vər·səl]
(geophysics)
A reversal of the polarity of the earth's magnetic field that has occurred at about one-million-year intervals.
References in periodicals archive ?
Experts said that the sun's magnetic reversal began in 1997 and was predicted to end in 2013.
This was problematic, because the most recent magnetic reversal occurred 780,000 years ago.
Although polar CMEs make up only 16 percent of all CMEs on the sun, they are the ones most important for the magnetic reversals.
By proving that magnetic reversal can take place in femtosecond timeframes, researchers have seen the potential for ultra fast and ultra dense magnetic data storage systems.
However, the magnetization of rocks as they are formed provides records, like a tape recorder, of the succession of the magnetic reversals through time, ultimately yielding the definition of the magnetic polarity time scale with more than 300 reversals over the last 160 million years.
These so-called magnetic reversals take about 10,000 years from start to finish.
Scientists aren't sure why magnetic reversals happen.
The combination of magnetic data from the ocean basins and onland basalt piles upward of 4-km thick, provides a chance to link magnetic reversals to biostratigraphy and absolute ages from the exposed rock record, and to understand in detail the behaviour of the earth's magnetic field during the reversal process.
The head properties have improved to detect finer granularities of magnetic reversals through use of Magneto Resistive (MR) and Giant Magneto Resistive (GMR) heads.
And while magnetic reversals have occurred in the history of the Earth, about once every 400,000 years, there's no evidence that such an event harms any life on Earth, and the phenomenon is unlikely to occur in the next several thousand years.
The other part of the MT signal is the seafloor magnetic field - not the steady field trapped in lavas and used to identify magnetic reversals, but the magnetic field variations linked to ionospheric currents.
These consisted of magnetic reversals in the soil just above the skulls, measurements of the decay of the element argon in fossil-bearing soil, and the bones of extinct rodents and other ancient creatures found with the skulls.

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