The measurements made by the Cluster C3 and C1 spacecraft revealed the 2-D morphology and altitude distribution of the acceleration (electric) potential in the AAR, shown here by equipotential contours derived by combining data from both satellites. The pattern consists of two broad, U-shaped potential structures at higher level (pale green) and a narrower S-shaped potential structure located below (pale blue). For the first time it was possible to constrain the size and longevity of the electric fields in the acceleration regions. The data showed that the electric field structures measured at least 800 km across and remained stable for at least 5 minutes.
New insight into the auroral acceleration region