Maps of precipitating electron spectra characterized by Maxwellian and kappa distributions

摘要

Maps of characterized auroral electron spectra, developed using 8 years of particle spectrometer data from the Defense Meteorological Satellite Program (DMSP) suite of polar-orbiting spacecraft are presented. The electron spectra, which were sampled from both hemispheres, are categorized as either diffuse or accelerated. Diffuse spectra were best-fit with Maxwellian or kappa distributions, and accelerated spectra were identified as displaying characteristics of either monoenergetic or broadband acceleration. A total of 30 million spectra were characterized, with 47.05% being best-fit with Maxwellian distributions, 31.37% being best-fit with kappa distributions, 12.20% as monoenergetic, and 9.38% as broadband. The spectra from both hemispheres were then binned in MLAT-MLT using a bin size of (MLAT, MLT) = (1?, 0.25 h), for the ranges of 50? ≤ MLAT 70? and broadband spectra occurred within 75? < MLAT < 80? and the local time regions of 0600 < MLT < 1000 and 1300 < MLT < 1500. For K_p ≥ 2, coverage of accelerated spectra varied with K_p. For low levels of K_p, accelerated spectra, primarily monoenergetic spectra, predominated above 70?. With increasing activity, broadband spectra covered more of the daytime MLT sectors, while diffuse spectra (Maxwellian and Lorentzian) became increasingly frequent on the nightside due to the poleward expansion of the diffuse precipitation region.