Effect of the Theta Aurora on the Polar Thermosphere

The theta aurora is characterized by a transpolar auroral arc, connecting the dayside to the nightside auroral oval A high-resolution time-dependent model of the global thermosphere is used to estimate the effects of this transpolar arc on the polar thermosphere. A background ionospheric model is assumed, and a simple but physically plausible representation of the ionospheric conditions within the transpolar arc is "superimposed" on the background ionosphere. The thermospheric model is then solved both with and without the imposed transpolar arc to determine the arc's effects on the neutral gas. In particular, percentage changes in thermospheric mass density and temperature are computed. These percentage differences are significant and are seen to vary systematically with the level of the ionospheric density enhancement within the arc. A strong dependence on solar activity level is also noted.