Ionospheric Peaked Structures and Their Local Time, Seasonal, and Solar Activity Dependence Based on Global Ionosphere Maps

摘要

The total electron content (TEC) data from Global Ionosphere Maps are used to obtain the tidal modes through two-dimensional Fourier transform in both universal time and LT (local time) frames. In the LT frame, a north-south TEC asymmetry is observed along the longitude, where there is a large displacement of the geomagnetic equator from the geographic equator. The phases of tidal modes lead to a constructive or destructive interference of contributing tidal modes, producing different zonal waves and longitudinal peaked structures at different local time (t_(LT)). The summation of all nonmigrating zonal waves in the low-latitude region (geomagnetic latitude < 30°) produces a peaked structure with two to four major peaks at most local hours. The amplitude of this peaked structure in June solstice is smaller than those in other seasons. During solar maximum (minimum), the amplitude of peaked structure has a value ~20 (~12) TECu with two to four (one to three) peaks. The locations of peaked structures formed by the nonmigrating tides in 2006 (solar minimum) and in 2014 (solar maximum) are similar. The Weddell Sea Anomaly is found to have a density enhancement in the region from 135°E to 90°W and from 40°S to 80°S with an amplitude ~19.85 (~5.07) TECu during March equinox (December solstice) of solar maximum (minimum).