Calculations of height-integrated conductivity from 31 individual Dynamics
Explorer (DE 2) substorm crossings presented by Gjerloev and Hoffman [this
issue] are used to compile empirical models of the height-integrated Peders
en and Hall conductivities (conductances) in a bulge-type auroral substorm.
Global auroral images obtained by Dynamics Explorer 1 (DE 1) were used to
select substorms displaying a typical bulge-type emission pattern and each
individual DE 2 pass was positioned with respect to key features in the obs
erved emission pattern. The conductances were calculated for each DE 2 pass
using electron precipitation data and a monoenergetic conductance model. A
ll passes were divided into six different sectors, and average conductance
profiles were carefully deduced for each of these sectors. Using a simple b
oxcar filter, smoothed average sector passes were calculated and from linea
r interpolation between these, two-dimensional conductance models were comp
iled. The characteristics of our models are (1) the Hall conductance maximi
zes in the high-latitude part of the surge at 48 mho with a Hall to Pederse
n ratio of 2.4; (2) two channels of enhanced conductance are overlapping in
local time near midnight and are fairly separated in latitude; (3) the con
ductance has a sharp gradient at the high-latitude boundary in the premidni
ght sector while in the postmidnight sector a broad region of low conductan
ce stretches up to 10 degrees invariant latitude poleward of the local peak
; and finally, (4) the enhanced conductance region displays a characteristi
c broadening toward dawn primarily owing to a poleward shift of the high-la
titude boundary.