Mean winds, tides, and quasi-2 day wave in the polar lower thermosphere observed in European Incoherent Scatter (EISCAT) 8 day run data in November 2003

Abstract

Simultaneous European Incoherent Scatter (EISCAT) radar observations using two EISCAT radars, the Tromsoø (69.6°N, 19.2°E) UHF radar and the EISCAT Svalbard radar (Longyearbyen, 78.2°N, 16.0°E), were conducted for 8 consecutive days, from 11 to 19 November 2003, to study the lower thermospheric wind dynamics in the polar region. Altitude profiles of the amplitudes of the diurnal and semidiurnal components at Tromsø and Longyearbyen are similar. The semidiurnal amplitudes in the meridional and zonal components exhibit maxima at 105-107 km, with values of ∼70-90 m s -1. The semidiurnal phases vary with roughly a 30 km vertical wavelength between 98 and 110 km. The quasi-2 day wave (Q2DW) was not detected in the lower thermosphere at either Tromsø or Longyearbyen during the period, while it was found between 70 and 82 km in the mesosphere with the colocated Tromsø MF radar. This observational result suggests that in general, the Q2DW attenuates in the mesosphere and cannot penetrate into the lower thermosphere in winter. Ion drag acceleration of the wind is generally negligible below 107 km at Tromsø and below 118 km at Longyearbyen, but significant ion drag acceleration is found above these heights. A comparison of mean wind and tidal amplitudes and phases with National Center for Atmospheric Research thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model predictions for the period shows some agreement. Copyright 2005 by the American Geophysical Union.