Boundary-oriented electron precipitation model

A boundary-oriented model of the global configuration of electrons precipit ating into the polar ionosphere is presented. It provides the differential energy flux of precipitating electrons from 32 eV to 30 keV for five differ ent activity levels. Data from 12 years and eight DMSP spacecraft were inco rporated into the model. The defining characteristic of this model is that only observations similarly located relative to auroral boundaries (e.g., o bservations just equatorward of the open-closed boundary) are averaged toge ther. The model resulting from this approach more closely resembles instant aneous observations than previous efforts. A distinct polar cap surrounds a narrow auroral zone, transitions between different regions are appropriate ly sharp, and model spectra are more realistic. This increased fidelity wit h observation is a significant advantage for the model, broadening its appl icability. Also new is the calculation of both mean and median model spectr a. The mean is dominated by sporadic flux enhancements, where present, whil e the median resembles more commonly observed background fluxes, permitting both of these aspects to be addressed. Parameterization for activity is ba sed on the degree of magnetotail stretching, as indicated by the latitude o f the ion isotropy boundary. A variety of features can be discerned in the model. There is a large difference between the mean and median energy flux in regions where upward region Birkeland currents are commonly observed. Th e smooth similar to 1 to 10 keV precipitation seen at most local times, in the equatorward portion of the oval, is nearly absent in much of the aftern oon sector. Enhanced number fluxes are seen at the poleward edge of the ova l near midnight, likely due to the frequent presence of field-aligned burst s. Structured precipitation dominates the energy flux at all local times ex cept between dawn and noon, where the contribution from unstructured precip itation dominates. The total hemispheric energy flux due to mean spectra va ries with activity from 6 to 38 GW and exceeds the energy flux due to media n spectra by a factor of approximately 4, regardless of activity.