Abstract
Abstract. We investigate an unusual sharp boundary separating two plasma populations (inner magnetospheric plasma with high fluxes of energetic particles and plasma sheet) observed by the Cluster quartet near its perigee on 16 December 2003. Cluster was in a pearl-on-string configuration at 05:00 MLT and mapped along magnetic field lines to ~8–9 RE in the equatorial plane. It was conjugate to the MIRACLE network and the DMSP F16 spacecraft passed close to Cluster footpoint. The properties of the sharp boundary, repeatedly crossed 7 times by five spacecraft during ~10 min, are: (1) upward FAC sheet at the boundary with ~30 nA/m2 current density at Cluster and ~2000 nA/m2 at DMSP; (2) the boundary had an embedded layered structure with different thickness scales, the electron population transition was at ~20 km scale at Cluster (<7 km at DMSP), proton population had a scale ~100 km, while the FAC sheet thickness was estimated to be ~500 km at Cluster (~100 km at DMSP); (3) the boundary propagated in the earthward-eastward direction at ~8 km/s in situ (equatorward-eastward ~0.8 km/s in ionosphere), and then decelerated and/or stopped. We discuss the boundary formation by the collision of two different plasmas which may include dynamical three-dimensional field-aligned current loops.
Highlights
The energetic particle population in the inner magnetosphere and the radiation belts, organized by particle drifts, is known to be rather stable except for energetic particle injection intervals and magnetic storm times, when the major magnetic reconfigurations occur and the transport of plasma and energy is strongly enhanced (e.g. Friedel et al, 2001).Investigating the Cluster perigee passes during 2001–2006 we found several cases of sharp changes in the energetic particles flux which sometimes occur inside the radiation belt, at locations presumably mapped to equatorial distances of 6–10 RE
Field-aligned ion beams are clearly distinguished at the first boundary, Fig. 3c, at 02:18:30–02:19:00. These plasma observations show that the spacecraft crossed twice a boundary separating two different plasma populations: (1) hot radiation belt-like plasma and (2) relatively cold, plasma sheet-like plasma
In the present study we investigate the distinct dynamical plasma boundary observed simultaneously by Cluster, DMSP, and the IMAGE magnetometer array in the morning sector (∼05:00 MLT) of the inner magnetosphere at 8–9 RE radial distance in the equatorial plane
Summary
The energetic particle population in the inner magnetosphere and the radiation belts, organized by particle drifts, is known to be rather stable except for energetic particle injection intervals and magnetic storm times, when the major magnetic reconfigurations occur and the transport of plasma and energy is strongly enhanced (e.g. Friedel et al, 2001). Investigating the Cluster perigee passes during 2001–2006 we found several cases of sharp changes in the energetic particles flux which sometimes occur inside the radiation belt, at locations presumably mapped to equatorial distances of 6–10 RE. Some of these flux changes (about one order of magnitude) consisted of successive sharp decreases and increases separated by 2–10 min. To our knowledge this phenomenon has not been properly investigated in the literature before. Apatenkov et al.: Sharp dynamical boundary in inner magnetosphere morning sector at Cluster and DMSP
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
