Premium
Fabry‐Perot interferometer measurements of thermospheric neutral wind gradients and reversals at Arecibo
Author(s) -
Friedman J. F.,
Herrero F. A.
Publication year - 1982
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/gl009i007p00785
Subject(s) - airglow , thermosphere , zonal and meridional , midnight , atmospheric sciences , incoherent scatter , geology , equator , magnitude (astronomy) , atmosphere (unit) , geophysics , ionosphere , physics , geodesy , meteorology , astrophysics , astronomy , latitude
Direct measurements of the meridional neutral winds in the thermosphere with the Arecibo Observatory Fabry‐Perot Interferometer show the post‐midnight meridional wind reversal that was inferred from previous incoherent scatter radar ion‐drift data and airglow intensity maps, and observed in‐situ with the Atmosphere Explorer‐E satellite NATE experiment. Data are shown for three nights between October 29 and December 9, 1981. For this period, the meridional wind is observed to be northward after sunset, turning southward before midnight with velocities which often exceed 100 m/sec, and after midnight its direction reverses to northward for one to two hours. The post‐midnight reversal is recurrent, and propagates from the equator, as predicted ort the basis of previous meridional airglow intensity measurements. On some nights the reversal is observed only to the south of Arecibo. In those cases it is possible to measure the wind velocity gradient which is set up by the convergent flow. The night of 29/30 October 1981 shows a gradient of about (0.3m/s)/km associated with the reversal (00‐0100 LT). Two hours later (0300 LT) an equatorward propagating disturbance with speed of propagation of about 700 m/s is observed. The gradients associated with the disturbance and with the reversal are of the same order of magnitude, giving changes of more than 150 m/sec in a horizontal distance of 500 km. The velocity gradient changes direction as a consequence of the passage of the disturbance. The simultaneous meridional airglow intensity distributions follow the direction of the velocity gradient.