New insight into secular variation between MAGSAT and CHAMP/ØRSTED

Abstract

Over the two decades between 1980 to 2000, the secular variation of the Earth's magnetic field demonstrates rich behavior. Three geomagnetic jerks (sharp changes in the slope of the first time derivative of the geomagnetic field) were detected within this period: 1983 only seen at the southern hemisphere [Dowson et al., 1988; Kotzé et al., 1991], 1991 [Macmillan, 1996] and around 2000 [Mandea et al., 2000] most clearly seen in the first time derivative of the East component, dY/dt, at European observatories. The non'global extent of the jerks raises questions about the processes which cause it. In this study we developed models for the secular variation and core'surface flows over this period. These models were derived from magnetic observatory quietest monthly means and satellite data. Our resulting models reveal small scale secular variation structure.