Reducing the Backus effect given some knowledge of the dip-equator

P Ultré-Guérard (1) , M Hamoudi (2) , G Hulot (1)

1 IPGP - Institut de Physique du Globe de Paris
2 USTHB - Université des Sciences et de la Technologie Houari Boumediene = University of Sciences and Technology Houari Boumediene [Alger]

Geomagnetic field models computed from intensity measurements on or near the Earth's surface are plagued with strong errors known as the "Backus ef-fect". These errors are related to the mathematical non-uniqueness of the solution which can be theoretically removed by the knowledge of the dip-equator location. Here, we present. a new method for computing models using intensity data and additional information about the location of the dip-equator. We first give a numerical validation of this approach in an ideal case in which the dip-equator can be assumed to be perfectly located. We then show that in practice, updating a good past model of the field with a model of secular variation can constrain the location of the dip-equator sufficiently for our method to be useful. Implications for the planning of future satellite missions are briefly discussed.

Domains: Sciences of the Universe [physics]; Earth Sciences; Geophysics [physics.geo-ph]

P Ultré-Guérard, M Hamoudi, G Hulot. Reducing the Backus effect given some knowledge of the dip-equator. Geophysical Research Letters, 1998, 25 (16), pp.3201-3204. ⟨10.1029/98GL02211⟩. ⟨insu-01405111⟩