Global response of the ionosphere to atmospheric tides forced from below: Comparison between COSMIC measurements and simulations by atmosphere‐ionosphere coupled model GAIA

Abstract

This paper for the first time presents a detailed comparison between simulated and observed global electron density responses to different atmospheric tides forced from below. The recently developed Earth's whole atmospheric model from the troposphere to the ionosphere, called GAIA, has been used for the simulation of the electron density tidal responses. They have been compared with the extracted from the COSMIC electron density data tidal responses for the period of time October 2007 to March 2009. Particular attention has been paid to the nonmigrating DE3/DE2 and migrating DW1, SW2 and TW3 electron density responses. The GAIA model reproduced quite well the COSMIC DE3/DE2 responses. Both simulations and observations revealed three altitude regions of enhanced electron density responses: (1) an upper level response, above 300 km height, apparently shaped mainly by the “fountain effect”; (2) a response located near altitudes of ∼200–270 km, and (3) a lower thermospheric response situated near 120–150 km height. A possible mechanism is suggested for explaining the two lower level responses. For the first time the GAIA model simulations supported the observational evidence found in the COSMIC measurements that the ionospheric WN4 (WN3) longitude structure is not generated only by the DE3 (DE2) tide as it has been often assumed. As regards the comparison of the migrating DW1, SW2 and TW3 responses the obtained results clearly demonstrate that the GAIA model reproduce very well of the SW2 and TW3 COSMIC electron density responses. The only main discrepancy is seen in the migrating DW1 response; the observation does not support the splitting of the simulated response at both sides of the equator. This is due mainly to the difference between the SABER and GAIA SW2 tide in the lower thermosphere as it turned out that the DW1 electron density response strongly depends on the mean features of the lower thermospheric SW2 tide.

Tidal signatures of the thermospheric mass density and zonal wind at midlatitude: CHAMP and GRACE observations

“…Hagan et al (2009) reported the existence of stationary planetary wave-4 (SPW4) oscillation in the upper mesosphere and lower thermosphere (MLT) region, caused by the nonlinear interaction between DE3 and the migrating tide DW1. Since then, the importance of stationary planetary waves, SPW4/SPW3, contributing to the longitudinal WN4/WN3 patterns in the upper atmosphere, has also been supported by both model simulations (e.g., Oberheide et al, 2011a;Pancheva et al, 2012) and in situ observations (e.g., Kil et al, 2010;Lühr and Manoj, 2013;Xiong and Lühr, 2013;Chang et al, 2013).…”

Satellite observations of middle atmosphere–thermosphere vertical coupling by gravity waves

“…It should be noted that the sampling time step of CHAMP data is also 10 s and the response function for CHAMP is the same as for GOCE. Following Park et al (2014), to avoid effects caused by equatorial plasma bubbles (e.g., Illés-Almár et al, 1998;Park et al, 2010) and to avoid artificial fluctuations due to the combination of low background level and CHAMP density accuracy (Liu et al, 2005), we consider only CHAMP data between 09:00 and 18:00 LT. Also, observations during disturbed periods (Kp > 4.0) are not considered.…”

Nonmigrating tidal signatures in the magnitude and the inter-hemispheric asymmetry of the equatorial ionization anomaly

“…The combined amplitudes of these two resulting components can be comparable with that of the DE3 (Oberheide et al, 2011). Furthermore, based on observations from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites and on simulations with the Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy (GAIA), Pancheva and Mukhtarov (2011), Pancheva et al (2012) showed the important contribution of the stationary planetary waves, SWP4/SWP3, to the WN4/WN3 ionospheric structures as well as the dependence of the WN4/WN3 hemisphere asymmetry on the SE2/SE1 tides.…”