Dynamic fluid-kinetic (DyFK) modeling of auroral plasma outflow driven by soft electron precipitation and transverse ion heating

We apply a recently developed dynamic fluid-kinetic (DyFK) model to simulat e and investigate the effects of soft auroral electron precipitation and pe rpendicular ion heating by waves on the plasma outflow along auroral field lines. The DyFK model is constructed by coupling a fluid ionospheric model for the region from 120 to 800 km to a semikinetic treatment for topside th rough several R-E altitude region. This approach, which is described in det ail here, allows a partially self-consistent description of the plasma tran sport along high-latitude flux tubes where both low-altitude ionospheric he ating and ionization production and loss as well as high-altitude energizat ion and kinetic effects are incorporated and stressed. In the present work, we investigate the combined effects of the F region plasma production and electron heating by soft auroral electron precipitation and ion perpendicul ar wave heating at high altitudes, which produces ion conics. The auroral e vent simulated here involves 1.5 hours of moderate soft electron precipitat ion and relatively weak ion cyclotron waves along the magnetic field lines. The simulations reveal the F region electron heating and ionization by the soft electron precipitation, driving a topside of upflow of up to 10(9) cm (-2) s(-1) below 1000 km within 30 min after the electron precipitation is turned on. The enhanced O+ upflow plumes would be still gravitationally bou nd in the absence of further energization at higher altitudes. However, the synergistic effects of the increased upwelling ion supply driven by the pr ecipitation and the wave-driven ion heating at higher altitudes combine to enhance O+ bulk outflow by an order of magnitude above the baseline polar w ind level to a net outflow flux of 10(8) ions cm(-2) s(-1) with a density o f 10 ions cm(-3) and bulk velocity of 12 km s(-1) at 3 R-E altitude. Variou s O+ conic velocity distributions develop within 10 min after transverse he aling is initiated, and their characteristic energies saturate at approxima tely 10 eV for the peak wave-induced heating rates of 10(-14) ergs s(-1) at 2 R-E here. H+ is also affected by the increases of O+ due to H+- O+ colli sional drag in the 1000 - 4000 km altitude transition region. H+ flow is mu ch less affected by the wave heating because of the faster transit times th rough the high-altitude wave heating zone and the lower H+ perpendicular he ating rates which were incorporated here. The H+ bulk flow consists of a fl ux of 10(8) ions cm(-2) s(-1), a density of 4 ions cm(-3), and a velocity o f 30 km s(-1) at 3 R-E altitude.