Auroral electron energy spectra

Observations of differential energy spectra of electrons above a weak aurora at Fort Churchill are presented. Measurements were made at altitudes between 180 and 250 km using an electrostatic analyzer and channeltron detector over the energy range 10 ev to 10 kev. It is shown that below about 100 ev scattering from the rocket was pronounced. Although between 1 and 10 kev the spectra can be well represented by power-exponential functions with maxima in the region 1–4 kev, between 1 kev and 100 ev the flux rises toward lower energies. An estimate of the number of secondaries in the energy region 100 ev to 1 kev generated by the higher energy primaries is made, and it proves to be too small to explain the observed electron flux at low energies. This flux is shown to vary so little with altitude that it is likely to be due to ambient electrons accelerated by electric fields.