Journal of Geophysical Research: Space Physics
American Geophysical Union
This is the first study in which a physical ionospheric model (time-dependent ionospheric model (TDIM)) has been driven through a substorm using self-consistent magnetospheric convection electric field and auroral electron precipitation inputs. Both of these were generated from a simulation of a real 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 expansion dynamics is captured in a 1.5-hour time period. As a reference against which to compare this TDIM substorm simulation, a typical climatological TDIM simulation was carried out using standard statistical representations of the convection electric field and auroral oval. Note that these statistical representations are driven by the Kp 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 oval are used for the TDIM reference simulation. From the comparison of these two simulations, we find, as expected, the E region densities are different. However, these differences lead to factors of 2–4 differences in the integrated Hall and Pedersen conductivities. These conductivities, in turn, are crucial as an ionospheric boundary condition for magnetospheric MHD modeling. The F region spatial and temporal responses are complex and exhibit large differences, from tens of percents to factors of 4 in density and up to ±70 km in hmF2. These differences are all larger than typical experimental uncertainties. The day side and cusp variabilities are very sensitive to the convection pattern and are not well correlated to magnetic indices, such as the 3-hourly Kp 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 “boundaries” in the plasma convection and auroral precipitation lead to large differences in the local F region densities and in the locations of strong density gradients, both of which are relevant to space weather applications.
Sojka, J. J., R. W. Schunk, M. D. Bowline, J. Chen, S. Slinker, and J. Fedder (1997), Driving a physical ionospheric model with a magnetospheric MHD model, J. Geophys. Res., 102(A10), 22,209–22,220, doi:10.1029/97JA01650.