Investigation of decadal scale changes in the auroral oval positions using Magsat and CHAMP data

The magnetic field sources inside the Earth play an important role in determining the long-term patterns in space weather and influence the magnetic field variations from sources external to the Earth. For example, current systems in the auroral region, which produce large magnetic disturbances during sub-storms, are strongly ordered by the Earth's main magnetic field which are connected via that field to interactions with the solar wind high in the magnetosphere. It has been known for some time that geodynamo processes in the Earth's fluid outer core result in changes in the magnetic field, known as secular variation, that are most visible on decadal and longer time-scales. Observatory measurements over the past two centuries suggest the dipole moment has decreased by over 10% in that period. Some changes of the non-dipolar field are seen to vary even more rapidly. For example, the north dip-pole has shifted hundreds of kilometres over the past century and with increasing speed over the past two decades. We present the results of a search for decadal changes in the latitudinal extent of the auroral current system over the satellite era using a combination of Magsat (1979-80) and CHAMP (2000-10) magnetic data. One advantage of using these satellite data is that their polar orbits have excellent latitudinal resolution, which will help fix the extent of the auroral current systems