Rocket-based measurement of birkeland currents related to an auroral arc and electrojet

A rocket-borne experiment to study the currents associated with a quiet auroral arc was conducted at Fort Churchill, Canada, near 8 P.M. on February 26, 1969. The magnetic field in the vicinity of the arc was measured with a vector magnetometer, while a lunar-aspect sensor provided information on the orientation of the payload. Possible current configurations were inferred by constructing model current systems that reproduced the magneticfield variations measured along the flight path. The data are interpreted in terms of a model current system consisting of a northwestward electro jet and two oppositely directed Birkeland sheet currents, all lying in planes approximately parallel to the auroral arc. The current density integrated through the 16-km thickness of each Birkeland current sheet was ∼0.16 amp/m; the electro jet current was ∼6×103amp. Comparison of the model currents with the electron fluxes detected by a separate experiment aboard the same rocket indicates that the upward Birkeland current and the electro jet were approximately coincident with the auroral arc as defined by precipitating electrons, and that 2- to 18-kev electrons carried roughly half the upward Birkeland current. The over-all current configuration differs from theoretical models proposed by Boström and Atkinson.