Geomagnetic jerks as chaotic fluctuations of the Earth's magnetic field

• Published in: Geochemistry, geophysics, geosystems : G3 Vol. 14; no. 4; pp. 839 - 850
• Main Authors: Qamili, E., De Santis, A., Isac, A., Mandea, M., Duka, B., Simonyan, A.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01.04.2013; John Wiley & Sons, Inc
• Subjects: chaos; Chaos theory; Deterioration; Earth; ergodicity; Fluctuation; Fluctuations; Geomagnetic field; Geomagnetic fields; geomagnetic jerks; Geomagnetism; Magnetic fields; Magnetism; Mathematical models; Minima; Steady state
• ISSN: 1525-2027; 1525-2027
• DOI: 10.1029/2012GC004398

The geomagnetic field is chaotic and can be characterized by a mean exponential time scale < τ > after which it is no longer predictable. It is also ergodic, so time analyses can substitute the more difficult phase space analyses. Taking advantage of these two properties of the Earth's magnetic field, a scheme of processing global geomagnetic models in time is presented, to estimate fluctuations of the time scale τ. Here considering that the capability to predict the geomagnetic field is reduced over periods of geomagnetic jerks, we propose a method to detect these events over a long time span. This approach considers that epochs characterized by relative minima of fluctuations in time scale τ, i.e., those periods when a geomagnetic field is less predictable, are possible jerk occurrence dates. We analyze the last 400 years of the geomagnetic field (covered by the Gufm1 model) to detect minima of fluctuations, i.e., epochs characterized by low values of the time scale. Most of the well known jerks are confirmed through this method and a few others have been suggested. Finally, we also identify some short periods when the field is less chaotic (more predictable) than usual, naming these periods as steady state geomagnetic regime, to underline their opposite behavior with respect to jerks. Key PointsPredictive and definitive geomagnetic models diverge exponentially in timeA predictability time window of 5–9 years is found>The epochs when the predictability deteriorates coincide with jerk occurrences