ESA Cluster observes jet braking and plasma heating

On 3 September 2006, the four Cluster spacecraft were flying in tetrahedral formation through the centre of the magnetotail, about 96 000 km from Earth (roughly one quarter of the Earth-Moon distance). Their particle, electric and magnetic field instruments detected an Earthward-moving plasma flow in the plasma sheet region that was travelling at a maximum speed of more than 800 km/s. Cluster's detection of 'whistler waves' at this time provided the first confirmation that the magnetic field in the plasma was piling up, an effect which led to the heating and acceleration of electrons - a process known as betatron acceleration. More images, movies and captions at ESA