Predicting the Auroral Oval Boundaries by Means of Polar Operational Environmental Satellite Particle Precipitation Data

Abstract

New empirical Kp-based models for the equatorward and poleward boundaries of the auroral oval in the Northern and Southern Hemispheres were developed, with the purpose of reviewing the auroral ovals predicted by well-established Feldstein auroral oval model. The new models were derived from particle and energy flux measurements from six low-altitude (800-900 km) POES/MetOp satellites. The equatorward and poleward boundaries of the auroral oval were defined for four different particle types: electrons with energies < 20 keV, protons with energies < 20 keV, electrons with energies > 30 keV and protons with energies 30-80 keV.

Three different fitting methods were used to express the detected auroral oval boundaries as a function of Kp: a fourth-order polynomial fit, a direct least-squares ellipse fit and a second-order Fourier series fit. All three methods had major caveats and could only provide rough estimates for the auroral oval boundary locations. However, the Fourier series fit was chosen as the most suitable method, since it incorporated an asymmetry between the hemispheres for the low-energy electron oval.

Compared to the Feldstein model, the new models estimated much larger auroral ovals, with the equatorward boundary being located significantly lower, in both hemispheres. Although incorporating information about specific auroral particle precipitation zones, the new models did not provide a good estimate for aurora visibility from the ground. To further elaborate on these models, it will be necessary to take into account the difference in altitude between the spacecraft orbits and the visible aurora.