The Time Delay of the Ionospheric Response to the Ring Current Variation

The link between intensification of the ring current inflation rate and the variation of ionospheric electric fields during the long-lasted storms is discussed. The main features of the ionospheric response to the ring current variation observed by STAREand SABREare the following: (1) The ionospheric response has a time delay of 1-2 hours in the afternoon sector of MLTwhere the electric field increases as a near-exponentiasl function, while in other sectors there is no delay and no systematic increase of electric fields, but an enhanced state with fluctuations, can be found. (2) Opposite tendency of electric field variations often appears from STARE (70.2°N) and SABRE (65.8°N) observations. (3) In the STAREfield of view the magnitude of electric fields at lower latitude (70.2°N) is usually larger than that at higher latitude (71.8°N) during ring current increase events. These facts are consistent qualitatively with predictions of simple model of Zi and Shen, 1986. The results show that the ring current has an important influence on the magnetosphere-ionosphere coupling.