An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 5 Search : reversal
magnetic reversal
  وارونش ِ مغناتیسی   
vâruneš-e meqnâtisi

Fr.: inversion magnétique   

A change in the Earth's → magnetic field in which the → magnetic north pole is transformed into a → magnetic south pole and the magnetic south pole becomes a magnetic north pole. There are geological proofs indicating that the Earth's magnetic field has undergone numerous reversals of → polarity in the past. In the last 10 million years, there have been, on average, 4 or 5 reversals per million years. At other times, for example during the → Cretaceous era, there have been much longer periods when no reversals occurred. Over the past two centuries, Earth's magnetic field has weakened by 15%. Risks of a weak magnetic field include more deaths from cancer due to increased radiation, electrical grid collapse from severe solar storms, climate change, and temporary ozone holes.

magnetic; → reversal.

phase reversal
  واگردانی ِ فاز، وارونش ِ ~   
vâgardâni-ye fâz, vâruneš-e ~

Fr.: inversion de phase   

An angular shift in phase by 180°.

phase; → reversal.

polarity reversal
  وارونش ِ قطبیگی، واگردانی ِ ~   
v âruneš-e qotbigi, vâgardâni-ye ~

Fr.: inversion de polarité   

1) A change in the → polarity of Earth's magnetic field in which the north magnetic pole becomes the south magnetic pole and vice versa. Also known as geomagnetic reversal or magnetic reversal. Earth's magnetic field has reversed many times in the past and the time intervals between these changes are known as → polarity epochs.
2) The change in the polarity of the → solar magnetic field with the ending of each → solar activity cycle so that the North magnetic pole becomes the South and vice versa.

polarity; → reversal.

reversal
  وارونش، واگردانی   
vâruneš, vâgardâni

Fr.: inversion, interversion   

An act or instance of reversing. The state of being reversed. → phase reversal.

From → reverse + → -al.

time reversal
  وارونش ِ زمان   
vâruneš-e zamân

Fr.: renversement du temps   

A transformation operating on time in the equations of motion of a dynamical system in which t is replaced by -t.

time; → reversal.