Toward a better understanding of the global auroral electrodynamics through numerical modeling studies
1991 (English)In: Magnetospheric Substorms, Washington, DC: American Geophysical Union (AGU), 1991, 305-319 p.Chapter in book (Refereed)
Results from numerical model studies are presented focusing on various aspects of the auroral electrodynamics. Studies of specific events, by means of extensive sets of observations which are fed into a numerical model to provide snapshots of the global electrodynamics, have been conducted in parallel with theoretical model studies. This has proven to be an efficient way to obtain a better physical understanding of the events in general and of the interrelationships between the physical parameters in particular. Of special interest are the electrodynamical features of northward IMF phenomena, to which we pay particular attention in this review. Examples are presented of transpolar arc events with particular emphasis on the convection signatures and how these relate to the auroral distribution. The influence on the global potential distribution of localized Birkeland currents associated with transpolar arcs is shown to be quite different from that of the more extended large-scale NBZ currents. For the former case the potential pattern is typically of a two cell type with modifications showing up as a poleward expansion of one of the cells, a local electric field reversal or possibly an electric field reduction at the center of the arc depending on how the arc-associated currents close in the ionosphere. For the case with large-scale NBZ currents, presumably related to extended regions of dim auroral features, the potential pattern is shown to have two, three, or four large-scale cells depending on the ratio between the NBZ and the oval currents, on the sign of the IMF By, and on the ionospheric conductivity.Of importance to these studies are also the statistical properties of the global electric field, current, and conductivity distributions and the relation between these for various conditions, a subject that will be briefly discussed. The effect of parallel potential drops in regions of upward field-aligned current has been taken into account in the model by assuming a linear relationship between these. Distortions of the equipotential contours above the potential drop occur as a result of this assumption as illustrated by projecting the ionospheric potential to the magnetosphere.
Place, publisher, year, edition, pages
Washington, DC: American Geophysical Union (AGU), 1991. 305-319 p.
, Geophys. Monogr. Ser.
2704 Magnetospheric Physics: Auroral phenomena, 7843 Space Plasma Physics: Numerical simulation studies, 2411 Ionosphere: Electric fields and currents, 2788 Magnetospheric Physics: Storms and substorms, Magnetospheric substorms—Congresses
Fusion, Plasma and Space Physics
IdentifiersURN: urn:nbn:se:kth:diva-92038OAI: oai:DiVA.org:kth-92038DiVA: diva2:511948
NR 201408052012-03-252012-03-252012-03-25Bibliographically approved