Height-integrated conductivity in auroral substorms - 1. Data

We present height-integrated Hall and Pedersen conductivity (conductance) c alculations from 31 individual Dynamics Explorer 2 (DE 2) substorm crossing s. All are northern hemisphere (except one) nighttime passes which took pla ce from September 1981 to January 1982. Global auroral images are used to s elect 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 c alculated from electron precipitation data obtained by the low altitude pla sma instrument (LAPI) carried on DE 2 and the monoenergetic conductance mod el by Reiff [1984]. This method is shown to effectively minimize undesirabl e smearing of parameters in statistical substorm studies. Large spatial gra dients in the conductance profiles are common in high-latitude part of the premidnight substorm region. The conductances maximizes in the high-latitud e part of the surge with average Hall and Pedersen conductances of 38 and 1 8 mho respectively. During six different DE 2 passes we found Hall conducta nce peaks exceeding 100 mho in the high-latitude part of the surge or surge hem. These peaks are highly localized with a typical scale size of similar to 20 km and are associated with energetic (>10 keV) inverted V events. Ex cept in the low-latitude part of the auroral oval the Hall to Pedersen rati o equals or exceeds 1.0, and it peaks in the high-latitude part of the surg e where values of 3 or more are common. The latitudinal conductance profile s are strongly asymmetric and have a pronounced local time dependency.