Bi-Maxwellian Characterization of Energetic Electron Populations in Diffuse Aurora

We examine energetic electron distributions in the region of the diffuse aurora using a two-dimensional bi-Maxwellian model, applied to electron flux data at a single geomagnetic equator (L = 6.5). Electron flux is analyzed as a function of energy and pitch angle and transformed into velocity space to reconstruct the distribution function. An unweighted log-space least-squares fit of the bi-Maxwellian model to the reconstructed distribution yields a reduced residual measure of χ2 v = 1.000053, a mean absolute residual of |∆log10 f| = 0.0469 dex, an anisotropy factor, AT = 0.9886±0.0016, and no statistically significant bulk drift. These results show that, at this location, the bi-Maxwellian model reproduces the observed velocity-space structure with good quantitative accuracy and reveals a quasi-isotropic, near-equilibrium electron population.