March 18, 2010, 1:00 pm - 2:00 pm

March 18, 2010, 1:00 pm - 2:00 pm

Multi-spacecraft observations of auroral electron acceleration by Cluster

Colin Forsyth (Mullard Space Science Laboratory)

It has been long understood that in order to create bright aurora, magnetospheric particles must be accelerated into the ionosphere. This acceleration takes place in the "auroral acceleration region" (AAR), located a few Earth radii above the ionosphere. During recent years the orbit of the Cluster spacecraft has evolved such that the spacecraft pass through this auroral acceleration region close to perigee during the dayside season. This presents the opportunity to make multi-spacecraft measurements of this region for the first time. In this talk, I will briefly review previous spacecraft observations of the AAR, before presentinga case study of an upward auroral current region observed by Cluster in December 2009. During this event, Cluster 1 and Cluster 3 were approximately located on the same magnetic field-line but separated by 1000 km. During this event, the electron population was accelerated along the field-line between Cluster 1 and 3. Magnetic field observations confirm the presence of an upward current system. Based on these observations, the size of the length of the acceleration region is estimated.