Tehostekuvassa fysiikan laitosta etuoven suunnalta

3a. Testing the GAD model

Participating scientists

  • L.J. Pesonen, project leader
  • T. Veikkolainen, M.Sc.
  • J. Meert (University of Florida, USA)
  • D.A.D. Evans (Yale University, USA)
  • K. Korhonen (Geological Survey of Finland)

Project goals

To test the validity of Geocentric Axial Dipole (GAD) hypothesis for the geomagnetic field using five methods: (i) inclination analysis, (ii) PSV, (iii) reversal asymmetries, (iv) reversal transitions and (v) frequency of latitudinally sensitive sediments such as evaporites).

Fig.1: Inclination frequency method (Veikkolainen et al. 2013)
Fig.1: Inclination frequency analysis (Veikkolainen et al. 2013)
Fig.2: Paleosecular variation analysis (PSV)
Fig.2: Paleosecular variation analysis (PSV)
Fig.3: Evaporate method to estimate ND field (Evans, 2003)
Fig.3: Evaporate method to estimate ND field (Evans, 2003)
Fig.4: Reversal asymmetry analysis
Fig.4: Reversal asymmetry analysis

Highlights

Inclination frequency method suggests a near GAD - field during the Precambrian with ≤ 2 % quadrupole and 5% octupole field.

Since the inclination distribution of GAD with 17 % quadrupole (G2) and 3 % octupole (G3) model is similar to that of pure GAD, the method is non-unique and results must be verified using other methods.

Reversal asymmetry analysis, however, suggests that the GAD + G2 (17 %) + G3 (3 %) is not possible, but a field close to GAD is.

Spatiotemporal binning of paleomagnetic data must be observed with caution.

Recent publications

  • Veikkolainen, T., Evans, D.A.D., Korhonen, K., Pesonen, L.J. (2013). On the low-inclination bias of the Precambrian geomagnetic field. Precambrian Research, in press.
  • Veikkolainen, T., Pesonen, L., Korhonen, K., Evans, D.A.D. (2012). The Precambrian geomagnetic field has no prominent low-inclination bias. Supercontinent Symposium, Helsinki, Finland, September 25-28, 2013, University of Helsinki.
  • Veikkolainen, T., Pesonen, L., Korhonen, K. (2012). The reliability of the Geocentric Axial Dipole model as evaluated from the reversal asymmetry of the Precambrian geomagnetic field. Supercontinent Symposium, Helsinki, Finland, September 25-28, 2013, University of Helsinki.
  • Veikkolainen, T., Pesonen, L., Korhonen, K. (2012). Paleosecular variation and the validity of the Geocentric Axial Dipole theory. Supercontinent Symposium, Helsinki, Finland, September 25-28, 2013, University of Helsinki.
  • Veikkolainen, T., Pesonen, L.J., Evans, D.A.D., Korhonen, K. (2011). New Results from Testing the Geocentric Axial Model (GAD) of the Geomagnetic Field Using Inclination Data. AGU Fall Meeting, Moscone Center, San Francisco, California, USA, December 5-9, 2011, American Geophysical Union.