Comment on “Will the magnetic North Pole move to Siberia?”

Abstract

In a recent Eos article, Olsen and Mandea [2007] commented on the rapid motion of the north magnetic pole (NMP) and the ability of recent magnetic field models based on satellite data to give accurate positions for the magnetic poles. The most recent local survey to determine the position of the NMP, carried out in April 2007, confirms their observations concerning the movement of the NMP and supports their thesis that reference field models can now accurately locate the magnetic poles. We were able to observe at four locations all within approximately 100 kilometers of the estimated pole position. This small sample, plus one observation made in 2005, is sufficient to reveal that the position of the NMP on 29 April 2007 was 83.95°N, 121.02°W, with a positional uncertainty of approximately 40 kilometers (L.R. Newitt et al., manuscript in preparation, 2007). This is in close agreement with positions derived from recent spherical harmonic models that are based on satellite magnetic data. For example, the NMP position derived from the CHAOS model is within 35 kilometers of the observed position.

Magnetic flux expulsion from the core as a possible cause of the unusually large acceleration of the north magnetic pole during the 1990s

“…This phenomenon was first detected through local surveys [ Newitt and Barton , 1996; Newitt et al , 2002] and later in global geomagnetic models [ Mandea and Dormy , 2003]. According to the most recent direct observation of the NMP, made in April 2007, the NMP's drift rate has since stabilized at just over 50 km/yr [ Newitt and Chulliat , 2007; Newitt et al , 2009, hereafter NCO09]. It may even have started to decrease, as suggested by the recent xCHAOS geomagnetic field model which is based on data from the Ørsted and CHAMP satellites [ Olsen and Mandea , 2007a].…”