Ring Current Energy Input and Decay

Janet U. Kozyra and Michael W. Liemohn


A new view of the ring current as an active element in the geospace system has
emerged in which the ring current responds not only to changing convection
electric fields imposed by solar wind interactions but to internal dynamics of
the magnetosphere-ionosphere-atmosphere (geospace) system. Variations in the
plasma sheet density, temperature and composition, saturation of the polar cap
potential drop (and presumably the cross-tail potential drop), modifications to
the imposed convection potential in the inner magnetosphere due to ring current
shielding effects, the presence of a pre-existing ring current population,
storm-substorm coupling, and strong convection with and without accompanying
substorm activity all have an impact on the ring current strength, formation and
loss. All of these internal processes imply that the geoeffectiveness of a solar
wind driver cannot be predicted on the basis of the characteristics of the
driver alone but must reflect key aspects of the dynamically changing geospace
environment, itself. This review gives a summary of new information on ring
current input and decay processes focusing on implications for the global
geospace response to solar wind drivers during magnetic storms and on open
questions that can be addressed with new ENA imaging techniques.

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Space Science Reviews, 109 (1-4) 105-131, 2003