When the dipole geomagnetic field dwindles away

It is now widely accepted that the geomagnetic field changes sign from time to time, generally irregularly, this "reversal" being accompanied by a decrease in intensity. Study of these changes in the past geomagnetic field has been limited to consideration of the dipole field. Unfortunately, the non-dipole geomagnetic field is more significant than has been considered previously - not only in palaeo-magnetism (Facer, 1970), but perhaps in the future in exploration magnetic studies also.