Understanding the Earth's ionosphere as a fully sufficient source for magnetospheric plasma

One of the most significant questions remaining in space physics concerns the ultimate fate of ionospheric plasma outflows and their relative contribution to the plasma populations within the magnetosphere. A growing number of ionospheric outflow studies over the past two decades have cast serious doubt on the traditional view of solar wind as a dominant source of magnetospheric plasma. A unique approach combining data and modeling have been used here to demonstrate that the earth's ionosphere is fully capable of providing the magnetosphere with plasma at energies and densities that are consistent with observations.; The first detailed statistical analysis of pitch angle and energy distributions of polar wind (<3.5 eV) outflows has been performed using data from the Thermal Ion Dynamics Experiment (TIDE) on board the Polar spacecraft. A new method of accounting for spacecraft charging effects has been used, providing improved estimates of the true polar wind outflow characteristics.; The results of this polar wind analysis are used together with known cleft ion fountain (CIF) and auroral source characteristics as input to a single particle trajectory code that traces ion motion throughout magnetospheric electric and magnetic fields. The results of numerous model trajectories suggest that ion drifts through magnetospheric electric fields are capable of accelerating terrestrial ions out to the distant magnetotail where they are further accelerated to plasma sheet and ring current energies. Ion flow characteristics, energies, and densities as calculated from the model agree closely with observations. Polar wind from the dayside ionosphere appears to be the dominant source for magnetospheric H+ ions, while auroral ions play a surprisingly minor role in plasma sheet refilling and ring current formation. Cold populations (<50 eV) of ionospheric material appear to exist throughout much of the outer magnetosphere that would be difficult to detect with current orbiting particle instruments. Renewed efforts are needed throughout the space physics community to address the implications of the ionosphere the dominant source of plasma for the magnetosphere.