Ionization by energetic protons in Thermosphere-Ionosphere ElectrodynamicsGeneral Circulation Model

Originating in the magnetosphere and precipitating into the high-latitude i onosphere, energetic protons in the keV energy range are a common auroral p henomenon and can represent an important energy source for the auroral atmo sphere. In global models describing the ionosphere-thermosphere interaction , keV protons have always been neglected or treated as if they were electro ns. Here we investigate the effect of keV protons on both the ionospheric a nd thermospheric composition in the E region on a planetary scale. We prese nt a parameterization of electron and ion production rates induced by an in cident proton beam as a fast computational scheme for use in global models. The incident proton beam is assumed to have a Maxwellian distribution with characteristic energies between 1 and 20 keV. The parameterization is vali dated against a full proton transport code. By including these parameterize d electron and ion production rates in a one dimension-in-space (1D-in-spac e) Thermosphere-Ionosphere Global Mean Model, we show that proton precipita tion can cause a significant enhancement of the electron density, the major ion (O-2(+) and NO+) densities, and the nitric oxide density. As a result, the conductivities in the E region are also greatly increased. Using the T hermosphere-Ionosphere Electrodynamics General Circulation Model (TIE-GCM), we show that the proton precipitation, when added to the normal electron a urora, causes a large increase (up to 70%) in electron, O-2(+), and NO+ den sities over much of the auroral oval. The NO density is affected in a large r area owing to the long lifetime of NO on the nightside. This first study of the influence of protons on a planetary scale clearly shows the signific ant impact that auroral keV protons can have on the ionospheric and thermos pheric composition and the need to include proton precipitation in global m odels.