Earthward flowing plasmoid: Structure and its related ionospheric signature

Abstract

An earthward moving plasmoid has been observed on 28 October 2002 by the Cluster spacecraft with simultaneous auroral viewing by the IMAGE satellite. This offers the opportunity to ascertain the optical and the evolutional signatures in the ionosphere of the earthward moving plasmoid. The ionospheric signatures observed in this paper are not substorm-related. Both the ground-based measurements and IMAGE satellite auroral observations show the ionospheric signatures moving to lower latitudes, when the earthward moving plasmoid is observed by the Cluster spacecraft. The intensity of the current in the center of the plasmoid is found to be weaker than that in the adjacent region. Also, the directions of the current in the central part of the plasmoid, different from the background cross-tail current, are more field-aligned. Those facts are consistent with the tail current closes through the substorm-like current wedge, since the cross-tail current is blocked by the plasmoid. On the other hand, the current in the earthward plasmoid may close through the interhemisphere. In this paper we demonstrate that the magnetic structures, plasmoids and flux ropes, will transport flux and energy from the distant tail to the Earth.