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First measurements of tidal modes in the lower thermosphere by the EISCAT Svalbard radar
Author(s) -
van Eyken A. P.,
Williams P. J. S.,
Buchert S. C.,
Kunitake M.
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 - 10.1029/1999gl003687
Subject(s) - thermosphere , atmospheric tide , atmospheric sciences , geology , ionosphere , wavelength , mesosphere , radar , variation (astronomy) , geodesy , geophysics , physics , optics , astrophysics , stratosphere , telecommunications , computer science
First measurements by the EISCAT Svalbard Radar of ion velocities in the lower thermosphere show the presence of strong tidal or quasi‐tidal modes with periods of 24, 12 and 8 hours. The diurnal mode shows no variation of phase with height above 100 km. In contrast, the semidiurnal and terdiurnal modes show a steady variation of phase with height corresponding to vertical wavelengths of about 40 km and 30 km respectively. In addition there is evidence at 93 km, the lowest height measured, of a planetary wave with a period of 2–3 days.