Global ionospheric response to nonmigrating DE3 and DE2 tides forced from below

Abstract

[1] In this paper we present the global spatial structure and seasonal variability of the COSMIC electron density response to the forced from below DE3 and DE2 tides during the period January 2008 to March 2009. The COSMIC electron density at fixed altitudes and SABER temperatures were utilized in order to define the ionospheric DE3 and DE2 tidal response to the DE3 and DE2 temperature tides coming from below. The tidal waves from both data sets have been extracted by the same data analysis method. The latitude structure of the ionospheric response for heights up to 450–500 km is distributed on both sides of the dip equator at about ±30° modified dip latitude; above 500 km the response is approximately confined over the equator. Two altitude regions of enhanced ionospheric response are found: an upper level response (above 300 km) and a bottom level one (below 250 km); the two regions are separated by a narrow altitude zone with no tidal response. The different phase structure of the ionospheric response in both altitude regions suggests that (1) the upper level response is mainly due to the DE3/DE2 modulated vertical plasma drift and (2) the bottom level response is complex and, in all likelihood, is caused by more than one mechanism.