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Large lunar tidal effects in the equatorial electrojet during northern winter and its relation to stratospheric sudden warming events
Author(s) -
Yamazaki Yosuke
Publication year - 2013
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2013ja019215
Subject(s) - equatorial electrojet , amplitude , ionosphere , atmospheric sciences , geology , electrojet , environmental science , sudden stratospheric warming , climatology , stratosphere , geophysics , polar vortex , physics , earth's magnetic field , quantum mechanics , magnetic field
It has been known for many decades that lunar tidal effects in the equatorial electrojet are greatest during northern winter; the mechanism of which has never been identified. Recent findings of the lunar tidal amplification during stratospheric sudden warming (SSW) events raise the question: To what extent do SSWs contribute to the large lunar tide during northern winter? We use ground magnetometer data at Addis Ababa for the years 1958–2007 to determine the average M 2 lunar tide in the equatorial electrojet at different seasons. When all the data are included, the amplitude of the lunar tide is largest during northern winter. However, when only the data for non‐SSW winters are used, the amplitude during northern winter is not significantly larger than during other seasons. The M 2 amplitude during SSW events is approximately 3 times as large as that for non‐SSW winters, and it considerably increases the amplitude of the average lunar tide during northern winter. The M 2 phase is not significantly affected by SSW events. These results indicate that the occurrence of SSW events significantly modulates the seasonal pattern of lunar tidal effects on the ionosphere.