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We compare the ionospheric electron precipitation morphology and power from a\udglobal MHD simulation (GUMICS-4) with direct measurements of auroral energy\udflux during a pair of substorms on 28-29 March 1998. The electron\udprecipitation power is computed directly from global images of auroral light\udobserved by the Polar satellite ultraviolet imager (UVI). Independent of the\udPolar UVI measurements, the electron precipitation energy is determined from\udSNOE satellite observations on the thermospheric nitric oxide (NO) density.\udWe find that the GUMICS-4 simulation reproduces the spatial variation of the\udglobal aurora rather reliably in the sense that the onset of the substorm is\udshown in GUMICS-4 simulation as enhanced precipitation in the right location\udat the right time. The total integrated precipitation power in the GUMICS-4\udsimulation is in quantitative agreement with the observations during quiet\udtimes, i.e., before the two substorm intensifications. We find that during\udactive times the GUMICS-4 integrated precipitation is a factor of 5 lower\udthan the observations indicate. However, we also find factor of 2-3\uddifferences in the precipitation power among the three different UVI\udprocessing methods tested here. The findings of this paper are used to\udcomplete an earlier objective, in which the total ionospheric power\uddeposition in the simulation is forecasted from a mathematical expression,\udwhich is a function of solar wind density, velocity and magnetic field. We\udfind that during this event, the correlation coefficient between the outcome\udof the forecasting expression and the simulation results is 0.83. During the\udevent, the simulation result on the total ionospheric power deposition agrees\udwith observations (correlation coefficient 0.8) and the <i>AE</i> index (0.85)

Precipitation and total power consumption in the ionosphere: Global MHD simulation results compared with Polar and SNOE observations