Magnetic poles and dipole tilt variation: GFZ

Magnetic poles and dipole tilt variation over the past decades to millennia

Introduction

Supplementary material for EPS article "Magnetic poles and dipole tilt variation over the past decades to millennia" by M. Korte and M. Mandea. The material consists of:

the geomagnetic and magnetic pole locations from 7000 BC to A.D. 2006.6
mpeg animations showing the changes of the poles and the radial geomagnetic field centered on the northern and southern hemisphere respectively.

The position of the magnetic poles is mainly of interest at the Earth's surface, while we investigate the field morphology generating these poles at the CMB. The animations show the radial field at the CMB with the TC indicated by a circle. For reference, the continent outlines are overlain, and these and the TC circle represent the area at the Earth's surface which is influenced by the respective areas of the core field if we assume no significant influences across the borders of a cone from the center of the Earth. This allows us to include the position of the magnetic poles at the Earth's surface in the same figures.

The data basis are published continuous geomagnetic field models covering different time intervals. North and south geomagnetic and magnetic pole locations were determined from these models. For the animations, model predictions were calculated on a regular global grid in evenly spaced time intervals and displayed as color-coded contour plots. Positions of magnetic and geomagnetic poles at the Earth's surface and the trace of the inner core tangent cylinder at the core-mantle boundary are superposed.

Producing grid values from model coefficients and plotting were done using the programs magmap and color by R.L. Parker.

Individual plots were combined to animations using the Berkely mpeg encoder.

References

Korte, M. and M. Mandea, Magnetic poles and dipole tilt variation over the past decades to millennia, Earth Planets Space, 60, 937-948, 2008.
Jackson, A., A. Jonkers, and M. Walker (2000), Four centuries of geomagnetic secular variation from historical records, Phil. Trans. R. Soc. Lond. A, 358, 957-990.
Korte, M. and C.G. Constable (2005): Continuous geomagnetic field models for the past 7 millennia: 2. CALS7K. Geochem., Geophys., Geosys. , 6(2), Q02H15, doi:10.1029/2004GC000801. (Model available at EarthRef.org digital archive or CALS7K Model site of GFZ Potsdam).
Sabaka, T.J., N. Olsen, and M.E. Purucker (2004), Extending comprehensive models of the Earth's magnetic field with Ørsted and CHAMP data, Geophys. J. Int., 159, 521-547. (Model available at GSFC NASA).
Olsen, N., H. Lühr, T.J. Sabaka, M. Mandea, M. Rother, L. Toffner-Clausen and S. Choi (2006): CHAOS - A model of the Earth's magnetic field derived from CHAMP, OØrsted and SAC-C magnetic satellite data. Geophys. J. Int., 166, 67-75. (Model available at CHAOS Model site of GFZ Potsdam).

Download

File	Format	Size	Date	Contents
CHAOS_poles	zipped ASCII data	0,7KB	Mar 2008	Geographic latitudes and longitudes of north and south geomagnetic and magnetic poles from CHAOS model (Olsen et al., 2006).
CM4_poles.zip	zipped ASCII data	1,2KB	Mar 2008	Geographic latitudes and longitudes of north and south geomagnetic and magnetic poles from CM4 model (Sabaka et al., 2004).
GUFM1_poles.zip	zipped ASCII data	7.0KB	Mar 2008	Geographic latitudes and longitudes of north and south geomagnetic and magnetic poles from gufm1 model (Jackson et al., 2000).
CALS7K.2_poles.zip	zipped ASCII data	78KB	Mar 2008	Geographic latitudes and longitudes of north and south geomagnetic and magnetic poles from CALS7K.2 model (Korte and Constable, 2005).
Br_CM4_N.mpg	Video stream data	1,7MB	Okt 2007	Animation: Radial magnetic field at the core-mantle boundary from the CM4 model [Sabaka et al., 2004] for the northern hemisphere with locations of magnetic (yellow star) and geomagnetic (green cross) poles at the Earth's surface. The rotation axis, i.e. geographic pole is marked by a black dot, the inner core tangent cylinder at the core-mantle boundary or projected to the Earth's surface by a white circle.Scalar data and model predictions.
Br_CM4_S.mpg	Video stream data	1.4MB	Okt 2007	Animation: Radial magnetic field at the core-mantle boundary from the CM4 [Sabaka et al., 2004] model for the southern hemisphere with locations of magnetic (yellow star) and geomagnetic (green cross) poles at the Earth's surface. The rotation axis, i.e. geographic pole is marked by a black dot, the inner core tangent cylinder at the core-mantle boundary or projected to the Earth's surface by a white circle.
Br_gufm1_N.mpg	Video stream data	7.2MB	Okt 2007	Animation: Radial magnetic field at the core-mantle boundary from the gufm1 model [Jackson et al., 2000] for the northern hemisphere with locations of magnetic (yellow star) and geomagnetic (green cross) poles at the Earth's surface. The pole marks have tails from their previous positions during the preceding 50 years. The rotation axis, i.e. geographic pole is marked by a black dot, the inner core tangent cylinder at the core-mantle boundary or projected to the Earth's surface by a white circle.
Br_gufm1_S.mpg	Video stream data	5.8MB	Okt 2007	Animation: Radial magnetic field at the core-mantle boundary from the gufm1 model [Jackson et al., 2000] for the southern hemisphere with locations of magnetic (yellow star) and geomagnetic (green cross) poles at the Earth's surface. The pole marks have tails from their previous positions during the preceding 50 years. The rotation axis, i.e. geographic pole is marked by a black dot, the inner core tangent cylinder at the core-mantle boundary or projected to the Earth's surface by a white circle.
Br_CALS7K_N.mpg	Video stream data	12MB	Okt 2007	Animation: Radial magnetic field at the core-mantle boundary from the CALS7K.2 model [Korte and Constable, 2005] for the southern hemisphere with locations of magnetic (yellow star) and geomagnetic (green cross) poles at the Earth's surface. The pole marks have tails from their previous positions during the preceding 500 years. The rotation axis, i.e. geographic pole is marked by a black dot, the inner core tangent cylinder at the core-mantle boundary or projected to the Earth's surface by a white circle.
Br_CALS7K_S.mpg	Video stream data		Okt 2007	Animation: Radial magnetic field at the core-mantle boundary from the CALS7K.2 model [Korte and Constable, 2005] for the southern hemisphere with locations of magnetic (yellow star) and geomagnetic (green cross) poles at the Earth's surface. The pole marks have tails from their previous positions during the preceding 500 years. The rotation axis, i.e. geographic pole is marked by a black dot, the inner core tangent cylinder at the core-mantle boundary or projected to the Earth's surface by a white circle.