Modelling composition changes in F-layer storms

A coupled thermosphere-ionosphere-plasmasphere model CTIP is used to simulate storm changes in the ionosphere. The simulations cover a period of 72 hours, starting with imposed high-latitude energy inputs (particle precipitation and electric fields) that represent a moderately severe geomagnetic storm (K-p 5) lasting for 12 h. Equinox and solstice conditions are studied. We give particular attention to comparing changes in peak electron density, N(m)F2, to those of the [O/N-2] concentration ratio of the neutral air.During the first few hours of the storm, large perturbations are produced by strong meridional winds. After that initial phase, we find that the changes of N(m)F2 and of [O/N-2] ratio correspond closely, the composition changes being produced by the thermospheric "storm circulation", as in the "composition bulge" theory of Fuller-Rowell et al. (1994). The simulations reproduce the general form of the seasonal variations in the changes of N(m)F2 at mid-latitudes as derived from worldwide ionosonde data. Some storm effects at sub-auroral latitudes are caused by movement and infilling of the ionospheric trough. We conclude that the composition change theory accounts for the major features of F-layer storm behaviour at midlatitudes. (C) 1997 Elsevier Science Ltd. All rights reserved

Future Directions for Whole Atmosphere Modeling: Developments in the Context of Space Weather

Coupled Sun‐to‐Earth models represent a key part of the future development of space weather forecasting. With respect to predicting the state of the thermosphere and ionosphere, there has been a recent paradigm shift; it is now clear that any self‐respecting model of this region needs to include some representation of forcing from the lower atmosphere, as well as solar and geomagnetic forcing. Here we assess existing modeling capability and set out a road map for the important next steps needed to ensure further advances. These steps include a model verification strategy, analysis of the impact of nonhydrostatic dynamical cores, and a cost‐benefit analysis of model chemistry for weather and climate applications

Ionospheric troughs in Antarctica

We report here the first observations of the dynamics of both the mid-latitude and high-latitude troughs made by the Advanced Ionospheric Sounder (AIS) at Halley Station, Antarctica (76° S, 27° W; invariant lat. 61°). This experiment is part of a major international project1 to study the sub-auroral ionosphere and its associations with the magnetosphere. Our analysis provides an accurate quantitative description of the latitudinal movements of these features and the first results delineating the orientation of the poleward edge of the mid-latitude trough. These results show that the AIS has a much greater potential for monitoring large scale ionospheric structures and for tracking their motions than more conventional radio wave experiments