Height‐integrated conductivity in auroral substorms: 1. Data

We present height‐integrated Hall and Pedersen conductivity (conductance) calculations from 31 individual Dynamics Explorer 2 (DE 2) substorm crossings. All are northern hemisphere (except one) nighttime passes which took place from September 1981 to January 1982. Global auroral images are used to select substorms which display a typical bulge‐type auroral emission pattern and to organize the position of individual DE 2 passes with respect to key features in the emission pattern. The Hall and Pedersen conductances are calculated from electron precipitation data obtained by the low altitude plasma instrument (LAPI) carried on DE 2 and the monoenergetic conductance model by Reiff [1984]. This method is shown to effectively minimize undesirable smearing of parameters in statistical substorm studies. Large spatial gradients in the conductance profiles are common in high‐latitude part of the premidnight substorm region. The conductances maximizes in the high‐latitude part of the surge with average Hall and Pedersen conductances of 38 and 18 mho respectively. During six different DE 2 passes we found Hall conductance peaks exceeding 100 mho in the high‐latitude part of the surge or surge horn. These peaks are highly localized with a typical scale size of ∼20 km and are associated with energetic (>10 keV) inverted V events. Except in the low‐latitude part of the auroral oval the Hall to Pedersen ratio equals or exceeds 1.0, and it peaks in the high‐latitude part of the surge where values of 3 or more are common. The latitudinal conductance profiles are strongly asymmetric and have a pronounced local time dependency.