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Concept
Ionospheric storm
Résumé
Ionospheric storms are storms which contain varying densities of energised electrons in the ionosphere as produced from the sun. Ionospheric storms are caused by geomagnetic storms. They are categorised into positive and negative storms, where positive storms have a high density of electrons and negative storms contain a lower density. The total electron content (TEC) is used to measure these densities, and is a key variable used in data to record and compare the intensities of ionospheric storms.
Ionospheric storm occurrences are strongly linked with sudden increases of solar wind speed, where solar wind brings energised electrons into the upper atmosphere of the Earth and contributes to increased TEC. Larger storms form global visibility of auroras. Auroras are most commonly seen in the arctic circle; however, large ionospheric storms allow for them to be visible in places such as the United States, United Kingdom, and Europe. The most intense ionospheric storm occurred in 1859, commonly named the “solar storm of 1859” or the “Carrington Event.” The Carrington Event was named after Richard Carrington, an English astronomer who observed the irregular sun activity that occurred during the Carrington Event. The intensity of the storm brought the visibility of the aurora even closer to the equator, reported to be seen in places near it such as Florida and the Caribbean. Ionospheric storms can happen at any time and location.
F-region and D-region ionospheric storms are also considered main categories of ionospheric storms. The F-region storms occur due to sudden increases of energised electrons instilled into Earth's ionosphere. The F-region is the highest region of the ionosphere. Consisting of the F1 and F2 layers, its distance above the earth's surface is approximately 200–500 km. The duration of these storms are around a day and reoccur every approximately 27.3 days. Most ionospheric abnormalities occur in the F2 and E layers of the ionosphere.
Source officielle
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