How Uncertainties in the Neutral Wind Affect Ionospheric Modeling

Abstract:

An ionospheric model relies on a number of input fields that are climatological in nature, being based on the statistical averaging of observations that have been classified or binned according to parameters such as season, solar activity level, geomagnetic activity level, and so on. One of the most important input fields for an ionospheric model, especially at mid-latitudes, is the neutral wind. The primary mechanism by which the neutral wind affects ionospheric densities is an induced upward or downward ion drift along the magnetic field lines. The magnitude of this effect depends upon the dip angle of the magnetic field; for this reason, the impact of the neutral wind is less in polar regions than at mid-latitudes. The quality of a model's output cannot be expected to be better than the quality of its inputs. It is unfortunate that observations of the neutral wind are relatively scarce, as compared for example with observations of the earth's electric field or auroral precipitation, and that the existing climatological models of the neutral wind are thus sharply limited in their accuracy. In this work, using Utah State University's Time Dependent Ionospheric Model (TDIM), we bring to light the degree to which a model's ability to simulate or forecast the ionosphere is hampered by an uncertain representation of the neutral wind.