Modelling the main ionospheric trough using the Electron Density Assimilative Model (EDAM) with assimilated GPS TEC

Abstract

Abstract. The main ionospheric trough is a large-scale spatial depletion in the electron density distribution at the interface between the high-and mid-latitude ionosphere. In western Europe it appears in early evening, progresses equatorward during the night, and retreats rapidly poleward at dawn. It exhibits substantial day-to-day variability and under conditions of increased geomagnetic activity it moves progressively to lower latitudes. Steep gradients on the trough-walls on either side of the trough minimum, and their variability, can cause problems for radio applications. Numerous studies have sought to characterize and quantify the trough behaviour.The Electron Density Assimilative Model (EDAM) models the ionosphere on a global scale. It assimilates observations into a background ionosphere, the International Reference Ionosphere 2007 (IRI2007), to provide a full 3-D representation of the ionospheric plasma distribution at specified times and days. This current investigation studied the capability of EDAM to model the ionosphere in the region of the main trough. Total electron content (TEC) measurements from 46 GPS stations in western Europe from September to December 2002 were assimilated into EDAM to provide a model of the ionosphere in the trough region. Vertical electron content profiles through the model revealed the trough and the detail of its structure. Statistical results are presented of the latitude of the trough minimum, TEC at the minimum and of other defined parameters that characterize the trough structure. The results are compared with previous observations made with the Navy Ionospheric Monitoring System (NIMS), and reveal the potential of EDAM to model the large-scale structure of the ionosphere.

A New Artificial Neural Network‐Based Global Three‐Dimensional Ionospheric Model (ANNIM‐3D) Using Long‐Term Ionospheric Observations: Preliminary Results

“…The trough weakens and moves poleward after sunrise (06–08 LT) and disappears completely by 10 LT. The observed local time variations in the location and strength of the trough are consistent with the main ionospheric trough between the middle and high latitudes reported in the literature (Lee et al, ; Moffett & Quegan, and Parker et al, ).…”

Statistical Analysis of the Main Ionospheric Trough Using Swarm in Situ Measurements

“…Many statistical analysis and modeling efforts have been made to provide certain insights into the trough characteristics, such as (1) LT variation: The trough is basically a nighttime feature, and the trough minimum position usually occurs at higher latitudes in the afternoon and migrates to lower latitudes with later LTs, reaching its equatormost position in the early morning sector (e.g., Ahmed et al, 1979;Deminov & Shubin, 2018;Grebowsky et al, 1983;Karpachev, 2003Karpachev, , 2019aKrankowski et al, 2009;Mallis & Essex, 1993;Oksman, 1982;Parker et al, 2018;Rodger, 2008;Werner & Prölss, 1997). (2) Seasonal and hemispheric variation: The afternoon and nighttime trough were observed to be better developed during equinoctial times, and the trough in the winter hemisphere is more prominent with broader width than that in the summer hemisphere (e.g., Horvath & Essex, 2003b;Lee et al, 2011;Voiculescu et al, 2006).…”