Ionospheric Conductances Due To Auroral Proton and Electron Precipitation Deduced From Image-fuv Observations.

The FUV instrument on the IMAGE (Imager for Magnetopause-to-Aurora Global Ex- ploration) satellite monitors the aurora in three different spectral regions. The Wide- band Imaging Camera (WIC) observes the molecular N2 LBH and the atomic NI emissions at 140-180 nm. The two channels of the Spectrographic Imager (SI) ob- serve the Doppler shifted Lyman- emission at 121.8 nm due to precipitating protons (SI12) and the electron auroral emission of OI at 135.6 nm (SI13). We calculate the Pedersen and Hall ionospheric conductances due to auroral particles based on FUV observations separately for the proton and electron precipitation. We first estimate the electron and proton energy fluxes from the FUV data, relying on energy degradation and auroral emission models. A two-stream model is used for the electron aurora while the proton aurora modeling is based on the direct Monte Carlo method, which gives a stochastic solution to the Boltzmann equations for the H+ - H beam. The electron energy is evaluated by combining observations from the three FUV instruments. For the proton energy, we use a statistical model based on in-situ particle measurements. Second, the particle energy and energy flux are used to estimate the ionization rates separately for protons and electrons, consistently with the energy degradation models. Finally, the electron and ion densities are estimated from ionization profiles, and the Pedersen and Hall conductances are calculated from fundamental equations. Appli- cations of the method to the distribution of the conductance at winter solstice in the course of substorm development over the north polar region will be illustrated.