The dayside high-latitude trough under quiet geomagnetic conditions: Radio tomography and the CTIP model

Abstract

Abstract. The dayside high-latitude trough is a persistent feature of the post-noon wintertime auroral ionosphere. Radio tomography observations have been used to map its location and latitudinal structure under quiet geomagnetic conditions (K p ≤2) near winter solstice. The trough is also a clear feature in the ion density distribution of the Coupled Thermosphere-Ionosphere-Plasmasphere model (CTIP) under similar geophysical conditions. Comparisons of the measured and modelled distributions show that the plasma production equatorward of the trough is mainly controlled by solar radiation, but there are also other processes maintaining the equatorward trough-wall that are open to debate. The poleward trough-wall is produced by particle precipitation, but the densities are significantly overestimated by the model. At the trough minimum the observed densities are consistent with low nighttime densities convecting sunward to displace the higher daytime densities, but this is not borne out by the CTIP model. The study shows the potential of combining radio tomography and modelling to interpret the balance of the physical processes responsible for large-scale structuring of the high-latitude ionosphere, and highlights the role of tomographic imaging in validating and developing physical models.

The role of the tongue‐of‐ionization in the formation of the poleward wall of the main trough in the European post‐midnight sector

“…Comparisons of the width of the tongue show that the modeled TOI (in both runs) covers a larger latitude range than that observed, but it must be borne in mind that the latitudinal dimension of the grid cells of the model is 2° while that of the observations is 0.25°. It has been shown in other studies comparing CTIP model output to observations [ Pryse et al , 2005], that the precipitation input is slightly too high and this would account for the differences in densities between the model run which includes the precipitation and the observations. These predictions, along with the EISCAT results lead us to the conclusion that the in situ precipitation played very little part, if any, in the production of the poleward trough wall observed in this case.…”

“…Tomography has been used in a recent study to parameterise the location and shape of the trough at midlatitudes over the UK [ Pryse et al , 2006a]. Obviously, both empirical and numerical models are important for predicting the structure of the ionosphere and neither can be used with any reliability if they haven't been verified by comparison with observations [e.g., Pryse et al , 2005].…”

A comparison of EISCAT and SuperDARN F‐region measurements with consideration of the refractive index in the scattering volume

“…Although this scale is quite large, smaller structures are expected to develop within these patches [Hosokawa et al, 2009]. Structure also exists in the region of the high-latitude ionospheric trough that, at least on the dayside, can be located poleward of the Hankasalmi SuperDARN radar location [e.g., Sojka et al, 1990;Pryse et al, 2005]. The poleward edge of the trough can produce an increase in electron density by an order of magnitude in a few tens of kilometers [e.g., Mitchell et al, 1995].…”

Modelling the tongue-of-ionisation using CTIP with SuperDARN electric potential input: verification by radiotomography

“…Fuller treatment of the precipitation is outside the scope of this investigation. However, it has a marked effect that needs consideration in future as indicated by Schoendorf et al (1996) and Pryse et al (2005).…”