Abstract Careful analyses during the past 5–6 years of particle and electric field signatures observed in association with the evening discrete arc have led to major advances in the basic understanding of the structure of the auroral electric potential. The origin of this basic potenital structure, which is inherent in the principle of kinetic plasma distributions in globally inhomogeneous magnetic configurations, is reviewed and examined. It is shown that, once the discrete arc potential structure is understood, this principle of arc formation can be applied to other geomagnetic configurations. In this way, a comprehensive theory of discrete auroral arcs of general configuration, including the theta aurora, can be constructed. Furthermore, completion of the auroral field-aligned current circuit in this theory leads to the hypothesis of downward parallel electric fields in the return current region away from the central portion of the discrete arc potential. Such downward parallel electric fields accelerate ionospheric electrons upward to form the return current and trap low-energy ions at the foot of the field line. It is shown that such trapping of ionospheric ions between the magnetic mirror below and the electric reflection above plays a crucial role in the heating and acceleration of ionospheric ions, which have been found to be an important source of magnetospheric plasma. Evidence for such downward parallel electric field signatures have been found in the last year or so.
Origin of auroral electric potential structures
Advances in Space Research ; 4 , 2-3 ; 491-498
1984-01-01
8 pages
Article (Journal)
Electronic Resource
English
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