Abstract
Abstract. We analyze tidal (diurnal, semidiurnal, terdiurnal, quarterdiurnal) phases and related wind shear in the mesosphere/lower thermosphere as observed by meteor radar over Collm (51.3∘ N, 13.0∘ E). The wind shear phases are compared with those of sporadic E (Es) occurrence rates, which were derived from GPS radio occultation signal-to-noise ratio (SNR) profiles measured by the COSMIC/FORMOSAT-3 satellites. At middle latitudes Es are mainly produced by wind shear, which, in the presence of a horizontal component of the Earth's magnetic field, leads to ion convergence in the region where the wind shear is negative. Consequently, we find good correspondence between radar derived wind shear and Es phases for the semidiurnal, terdiurnal, and quarterdiurnal tidal components. The diurnal tidal wind shear, however, does not correspond to the Es diurnal signal.
Highlights
In the lower ionospheric E region, shallow regions of high electron density are found, which are called sporadic E (Es) layers
The wind shear phases are compared with those of sporadic E (Es) occurrence rates, which were derived from Global Positioning System (GPS) radio occultation signal-to-noise ratio (SNR) profiles measured by the COSMIC/FORMOSAT3 satellites
The discrepancy arises because Es OR amplitudes are influenced by wind shear, and by background Es OR, which are dependent on meteor influx and background ionization in the course of a day
Summary
In the lower ionospheric E region, shallow regions of high electron density are found, which are called sporadic E (Es) layers. Arras: Quarterdiurnal signature in sporadic E and winds from the Horizontal Wind Model HWM07 (Drob et al, 2008) They found that wind shear theory satisfactorily explains the summer Es maximum, their metallic ion distribution maximises in summer, which is broadly in correspondence with qualitative results by Haldoupis et al (2007) who compared meteor rates with Es occurrence rates (OR). The Collm meteor radar measures mesospheric and lower thermospheric winds at altitudes of about 80–100 km since summer 2004 (Jacobi et al, 2007, 2009; Lilienthal and Jacobi, 2015) These observations have already been used for comparison with SDT, TDT, and QDT components in Es at these heights (Arras et al, 2009; Fytterer et al, 2013; Jacobi et al, 2018a), but for different time intervals, and without providing an overview of all tidal components together.
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