Large-scale double layer

This paper considers the structure of the large-scale double layer that results in a non-Maxwellian maximum in the electron distribution function in the current-discharge zone in the evening sector of the auroral magnetosphere. Closure of geomagnetic lines of force in this region is taken into account, along with the existence of a loss cone and instability of the ionospheric ion flux after discontinuity crossing. This instability is shown to result in trapping of the ions between conjugate double layers in the vertex region of a line of force.