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Auroral fading in ionosphere‐magnetosphere coupling model: Implications for possible mechanisms
Author(s) -
Janhunen P.,
Pulkkinen T. I.,
Kauristie K.
Publication year - 1995
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/95gl01799
Subject(s) - substorm , ionosphere , fading , magnetosphere , geophysics , plasma , physics , atmospheric sciences , coupling (piping) , precipitation , geostationary orbit , computational physics , geology , meteorology , materials science , astronomy , satellite , telecommunications , decoding methods , quantum mechanics , computer science , metallurgy
Sudden fading of the growth phase auroral arc and precipitation is sometimes observed just prior to substorm expansive phase onset. We can see a very similar phenomenon in a numerical ionosphere‐magnetosphere coupling model. In the numerical simulation, the fading occurs because the region of hot and dense magnetospheric plasma moves towards the Earth. At the same time, the plasma that maps to the poleward part of the fading area is cooled, which reduces precipitation there. The hot and dense plasma near geostationary orbit continues to precipitate, but to a lesser extent because it resides in a more dipolar field. Thus the fading phenomenon appears to to occur because the hot and dense plasma is temporarily “hidden” from the ionosphere. A few minutes later it moves tailward which causes the auroral brightening.