• Cluster;
  • MLR

[1] We present a case study of a magnetospheric line radiation (MLR) event observed simultaneously by Cluster 1 and Cluster 2 during a perigee passage at a radial distance of about 4 REand, at the same time, by the low-orbiting DEMETER satellite. This unique constellation enables us to analyze spatiotemporal variability of the phenomenon. Although the Cluster spacecraft are separated by as much as 0.7 L-shells, the observed wave pattern is the same on both. The analysis of B to E ratios indicates a quasiparallel propagation, which suggests that the waves cross the geomagnetic equator over a significant range of L-shells, at least 3.9–4.6. Simultaneous observations by the DEMETER satellite separated by about 1.8 hours in MLT from the Cluster spacecraft indicate a significant azimuthal extent of the source. The obtained results show that during the MLR event the same wave pattern is observed over a significant portion of the inner magnetosphere.