Electron measurements (18 keV–20 eV) in auroral events

Electron spectra measured on a rocket flight AMD-VB-34 through and over a series of auroral forms at Fort Churchill, Canada on 23 January 1974 show what can be described as inverted V events. Comparison with all-sky photographs identify clearly three of the events with three periods when the aurora was successively to the south of, underneath and to the north of the field line on which the rocket was located. In each of these events the electron spectrum changed from one resembling a Maxwellian of characteristic energy 3–4 keV on either side of the form to a nearly flat one out to 18 keV while the rocket was over the form. There was no indication of any spectral peaks in these spectra, which were confined to pitch angles of 70–90°. During descent the rocket moved slowly from over a quiet, fading arc to the equatorward side. Detailed electron observations show the spectrum returning to a Maxwellian distribution with steadily decreasing characteristic energy to 2 keV.