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Neutral winds in the lower thermosphere observed by WINDII during the April 4–5th, 1993 storm
Author(s) -
Zhang Shengpan P.,
Shepherd Gordon G.
Publication year - 2000
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 - 10.1029/2000gl000034
Subject(s) - thermosphere , geomagnetic storm , atmospheric sciences , storm , daytime , earth's magnetic field , latitude , altitude (triangle) , geomagnetic latitude , low latitude , environmental science , climatology , geology , ionosphere , physics , geophysics , geodesy , oceanography , magnetic field , geometry , mathematics , quantum mechanics
Data from a major geomagnetic storm in April 1993 were selected for the first WINDII study of storm‐induced neutral winds in the lower thermosphere between 90 and 200 km. The storm commenced at ∼1200 UT April 4th, when the Kp index increased from 1.3 to 7.7. The geomagnetic latitude range of WINDII measurements from the daytime O(¹S) emission reaches the southern geomagnetic pole. The wind exhibits a dramatic change during the storm. In the polar region the maximum velocity of ∼200 ms −1 at 140 km altitude on April 2nd increases to ∼650 ms −1 at 200 km on April 5th. Winds plotted in geomagnetic coordinates show the familiar two‐cell pattern in that winds are much stronger in the dusk sector than in the dawn sector. This pattern penetrates down to ∼130 km. During the recovery period on April 8th, winds at higher altitudes return to normal while the two‐cell pattern persists at lower altitudes. The thermospheric O(¹S) emission rate is severely depleted by the storm to half of its normal value.