Abstract
Abstract. The dynamics of the energy-latitude dispersed sub-keV trapped ions inside the ring current region, the so-called wedge-like dispersions structure, were statistically studied using Viking satellite data. Probabilities with/without these signatures at various local times in the dayside are obtained in terms of different time-lags from the substorm activity monitored by the AE index. The structure appears in the early morning sector within a few hours after the substorm, and it slowly propagates eastward while decaying with a time scale of several hours. The result qualitatively confirmed the previous model that the wedge-like dispersions are originated from past substorm-related plasma injections into the nightside ring current region, and that the dispersion is formed when these injected plasma slowly moves eastward to the dayside by the drift motion (E×B (eastward), grad-
Highlights
Satellites traversing inside the dayside ring current region frequently detect wedge-like energy-latitude dispersed dense trapped sub-keV ions far equatorward of the auroral region (Yamauchi et al, 1996a, 2005; Ebihara et al, 2001)
We employ backward superposed epoch analysis, i.e. we find out the timing of the nearest substorm activity before the Viking traversals, and arrange all Viking traversals in terms of given time-lags from the nearest substorm activity before the traversal
The minimum quiet probability should increase toward the evening sector because some wedge-like structure already stagnates in the morning sector when the magnetospheric electric field is weak
Summary
Satellites traversing inside the dayside ring current region frequently detect wedge-like energy-latitude dispersed dense trapped sub-keV ions far equatorward of the auroral region (Yamauchi et al, 1996a, 2005; Ebihara et al, 2001). The observed wedge-like energylatitude dispersed sub-keV ions may directly reflect nightside electromagnetic disturbances In this sense, they are probably the same as the regionally isolated sub-keV plasma sheetlike ions precipitating in the plasmasphere (Shelley et al, 1972; Sauvaud et al, 1981; Chappel et al, 1982; Newell and Meng, 1986). The latter is considered to be of substorm origin
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