ICI-III sounding rocket investigation of a Reversed flow event seen by the EISCAT Svalbard Radar

Abstract:

The Investigation of Cusp Irregularities (ICI)- III Sounding rocket was launched from Ny-Ålesund, Svalbard on December 3^rd, 2011. The aim of the ICI-III mission was to investigate the physics of RFE class of cusp flow events. ICI-III intersected the first RFE (RFE1) in a sequence of in total 3 consecutive RFEs seen by the EISCAT Svalbard Radar (ESR). The ESR and ICI-III were geographically looking at the same region of the ionosphere both at the time ICI-III entered RFE1 on its poleward boundary and left it on its equatorward boundary, hence ESR tracked the rocket perfectly on entering and leaving RFE1. ICI-III measured hence for the first time detailed flows and precipitation within an RFE with a resolution down to tens of meters.

The observations presented are used to test the various explanations that have been proposed as generation mechanisms for this phenomenon. The only consistent explanation that remains seems to be the theory suggested by Rinne et al. 2007, where an asymmetric version of the Southwood FTE twin cell model was proposed in which return flow develops predominantly on the poleward side of newly open flux since it is inhibited by the open-closed boundary (OCB) on the equatorward side to explain the RFE. By zooming into the RFE, detailed structure and dynamics within the RFE are revealed, previously unseen due to instrument resolution.