DRIVING A PHYSICAL IONOSPHERIC MODEL WITH A MAGNETOSPHERIC MHD MODEL

This is the first study in which a physical ionospheric model (time-de pendent ionospheric model (TDIM)) has been driven through a substorm u sing self-consistent magnetospheric convection electric field and auro ral electron precipitation inputs. Both of these were generated from a simulation of a red substorm event using the MHD model [Fedder et al. , 1995b]. Interplanetary magnetic field (IMF) data were available for 1.5 hours until the substorm breakup. Hence the substorm growth and ex pansion dynamics is captured in a 1.5-hour time period. As a reference against which to compare this TDIM substorm simulation, a typical cli matological TDIM simulation was carried out using standard statistical representations of the convection electric field and auroral oval. No te that these statistical representations are driven by the K-p index. This is a 3-hour index, yet the substorm growth and expansion occurs in 1.5 hours. Hence a static convection electric field and auroral ova l are used for: the TDIM reference simulation. From the comparison of these two simulations, we find, as expected, the E region densities ar e different. However, these differences lead to factors of 2-4 differe nces in the integrated Half and Pedersen conductivities, These conduct ivities, in turn, are crucial as an ionospheric boundary condition for magnetospheric MHD modeling. The F region spatial and temporal respon ses are complex and exhibit large differences, from tens of percents t o factors of 4 in density and up to +/-70 km in h(m)F(2). These differ ences are all larger than typical experimental uncertainties. The days ide and cusp variabilities are very sensitive to the convection patter n and are not well correlated to magnetic indices, such as the 3-hourl y K-p index, In the polar cap, the differences in the location of the tongues of ionization and the polar holes readily lead to factors of 2 -4 in local density differences, Differences in the locations of ''bou ndaries'' in the plasma convection and auroral precipitation lead to l arge differences in the local F region densities and in the locations of strong density gradients, both of which are relevant to space weath er applications.