Abstract
Abstract. We present results from co-ordinated measurements with the low altitude REIMEI satellite and the ESR (EISCAT Svalbard Radar), together with other ground-based instruments carried out in February 2006. The results mainly relate to the dayside cusp where clear signatures of so-called ion-dispersion are seen in the satellite data. The cusp ion-dispersion is important for helping to understand the temporal and spatial structure of magnetopause reconnection. Whenever a satellite crosses boundaries of flux tubes or convection cells, cusp structures such as ion-dispersion will always be encountered. In our case we observed 3 distinct steps in the ion energy, but it includes at least 2 more steps as well, which we interpret as temporal features in relation to pulsed reconnection at the magnetopause. In addition, fast variations of the electron flux and energy occurring during these events have been studied in detail. The variations of the electron population, if interpreted as structures crossed by the REIMEI satellite, would map near the magnetopause to similar features as observed previously with the Cluster satellites. These were explained as Alfvén waves originating from an X-line of magnetic reconnection.
Highlights
A change in the energy distributions of precipitating ions with latitude is known as ion-dispersion (Reiff et al, 1977)
The low energy ions and electrons are of magnetosheath origin and the cusp region, depending on the Interplanetary Magnetic Field (IMF) conditions, can be found in the range from 73◦ to 80◦ magnetic latitude and located near magnetic noon between 10:30–13:30 MLT (Newell and Meng, 1988)
Despite the emphasis of low energy particles, it should be mentioned that cusp energetic particle (CEP) events have been observed (Chen and Fritz, 2005)
Summary
A change in the energy distributions of precipitating ions with latitude is known as ion-dispersion (Reiff et al, 1977). B) Cusp structured ion-energy-dispersion (steps) produced in a transient/intermittent state by temporal features: Cusp structures were related to the crossing of 3 successive flux transfer events (FTEs) where each individual FTE signature could be identified by the jumps in the precipitating pattern with a short recurrence rate This is consistent with an intermittent reconnection taking place at the subsolar point on a short time scale (Escoubet et al, 1992). Stepped ion-dispersion at low-altitudes have been reported in association with poleward moving patches of elevated electron temperatures between the steps, detected by incoherent scatter radars (Lockwood et al, 1993a, 1995; Lockwood and Davis, 1996), and with poleward moving cusp/cleft auroral transients, observed by optical instruments (Farrugia et al, 1998; Pinnock et al, 1995) The latter is known as PMAFs (Poleward Moving Auroral Forms), which are ionospheric signatures of pulsed reconnection at the magnetopause (Sandholdt and Farrugia, 2007). Such waves propagating in the dayside auroral oval and in the vicinity of the cusp have been observed and identified by FAST satellites in narrow regions transverse to the field, typically of the order of 3 km and with highly non-sinusoidal irregular wave forms (Chaston et al, 1999)
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