Rocket measurement of auroral electron fluxes associated with field-aligned currents

A Nike-Tomahawk rocket was instrumented with a vector magnetometer and an array of particle detectors including an electron and proton energy spectrometer covering the energy range 0.5–20 keV in seven fixed intervals and measuring the pitch angle distribution from 0° to 180° as the rocket spun. The payload was launched from Poker Flat, Alaska, at 0722 UT on February 25, 1972, over a bright auroral band that evidently was the poleward electron aurora, beyond the trapping boundary. An upper limit to the measured proton flux was 106/cm² s sr keV. The energy spectrum of the electron flux measured during passage over the visible aurora always exhibited a peak within the measured energy range. During passage over the brighter auroral forms the peak shifted from ∼3 to ∼10 keV, the pitch angle distribution became peaked along B, and the intensity increased. Maximum fluxes of ∼3 × 108 el/cm² s sr keV were seen over the aurora, which reached ∼60 kR of λ5577. The electron flux in regions of maximum flux tended to be the most field-aligned in the energy interval showing the highest intensity.