Excitation and decay of magnetospheric lobe cell convection and its associated aurora

Abstract

We discuss multi‐instrument observations of the excitation and decay within a ∼10 min interval of a convection pattern typical of lobe cells, centered at ∼1230 MLT in the winter hemisphere. The plasma convection and its associated aurora were triggered by a rapid northward turning of the interplanetary magnetic field (IMF) monitored by near‐Earth spacecraft. The IMF stayed northward oriented ( Bx = −4 nT; By = 2–3 nT; Bz = 2–4 nT; clock angle = 30°–70°) for 8 min, before rotating back south. The optical instruments recorded the activation of an east‐west aligned auroral form near the latitude of the pre‐existing cusp aurora at ∼ 73° MLAT, which was followed by a smooth, 10‐min long poleward advance at an average speed of 0.4 km s−1, reaching 75° MLAT at its most expanded phase. Simultaneous CUTLASS radar and local magnetic data confirm the occurrence of a large reconfiguration of plasma convection involving a change from antisunward to sunward flow components in the vicinity of the cusp, consistent with the presence of a lobe cell.