IRF logo Project work in Space Plasma Physics
Examensarbete (20 p), spring 2006
Plasma flow along transpolar arcs

Student: Åsa Engström
Supervisor: Anita Kullen

Swedish Institute of Space Physics, Uppsala
Department of Astronomy and Space Physics, Uppsala University

Completed summer 2006


Strong E-field peaks are associated with electrons accelerated by parallel E-fields. High energetic electrons can cause discrete auroral arcs in the auroral oval as well as along the so called polar arcs occurring in the polar cap. According to Haerendel (1992) the discrete auroral arcs have an important role in transporting a surplus of energy out of the magnetosphere. Magnetic field lines, withfootprints on the auroral oval, map to the plasma sheet. Therefore the plasma flow is sunward at the auroral oval. To get an image of how the plasma flux in the ionosphere is related to discrete arcs, data from the Cluster satellites have been studied. One of the main objectives is to investigate the contribution of plasma flow caused by strong E-peaks to the plasma convection in the ionosphere. We find that the particle flux is in many cases in anti-sunward direction and that the particle flux peaks do, in most cases, contribute very little to the netto particle flux. This indicates that maybe the discrete arcs do not have such animportant role for the particle flux transport. We also examine transpolar arcs. Resent results show that the particle flux of nightside extension of the transp olar arcs is in anti-sunward direction (Liou et al, 2005). Our results confirm that there exist transpolar arc cases where the particle flux is anti-sunward.



Anita Kullen

last modified onThursday, 24-Aug-2006 13:30:44 CEST