Plasma measurements in pulsating auroras

Plasma probe experiments consisting of a Langmuir probe and a hemispherical gridded analyzer were flown on each of two Black Brant rockets during the pulsating aurora campaign in Canada in February, 1980. Electron temperature, suprathermal electron flux, and electron density profiles were obtained up to altitudes of approximately 150 km. The peak electron densities at 120 km of about 2 × 10 5 cm −3 are consistent with primary particle fluxes having Maxwellian distributions with a characteristic energy of about 2 keV. The integral flux of secondary electrons, with energies greater than 4 eV, increased with altitude and reached fluxes of 3.0 × 10 7 and 1.7 × 10 9 cm −2 s −1 sr −1 on the two flights. A close correlation was found between the optical pulsations and pulsations in the suprathermal flux which were 3 times the background flux. Pulsations in the electron density were barely detectable (< 20%) on only one flight. The observations support a magnetospheric flux limiting mechanism for these pulsating auroras rather than an ionospheric feedback model.