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Height‐integrated conductivity in auroral substorms: 2. Modeling

2000; American Geophysical Union; Volume: 105; Issue: A1 Linguagem: Inglês

10.1029/1999ja900353

2156-2202

J. W. Gjerloev, R. A. Hoffman,

Earthquake Detection and Analysis

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 Pedersen 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 observed emission pattern. The conductances were calculated for each DE 2 pass using electron precipitation data and a monoenergetic conductance model. All passes were divided into six different sectors, and average conductance profiles were carefully deduced for each of these sectors. Using a simple boxcar filter, smoothed average sector passes were calculated and from linear interpolation between these, two‐dimensional conductance models were compiled. The characteristics of our models are (1) the Hall conductance maximizes in the high‐latitude part of the surge at 48 mho with a Hall to Pedersen 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 conductance has a sharp gradient at the high‐latitude boundary in the premidnight sector while in the postmidnight sector a broad region of low conductance stretches up to 10° invariant latitude poleward of the local peak; and finally, (4) the enhanced conductance region displays a characteristic broadening toward dawn primarily owing to a poleward shift of the high‐latitude boundary.