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Nonlinear Processes in Geophysics An interactive open-access journal of the European Geosciences Union
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Volume 21, issue 2
Nonlin. Processes Geophys., 21, 347–356, 2014
https://doi.org/10.5194/npg-21-347-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Multifractional Brownian motions in geosciences

Nonlin. Processes Geophys., 21, 347–356, 2014
https://doi.org/10.5194/npg-21-347-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 03 Mar 2014

Research article | 03 Mar 2014

Latitudinal variation of stochastic properties of the geomagnetic field

J. A. Wanliss1, K. Shiokawa2, and K. Yumoto3 J. A. Wanliss et al.
  • 1Presbyterian College, 503 South Broad Street, Clinton, SC 29325, USA
  • 2Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8601, Japan
  • 3Space Environment Research Center, Kyushu University, 53 6-10-1 Hakozaki, Higashi-ku Fukuoka, 812-8581, Japan

Abstract. We explore the stochastic fractal qualities of the geomagnetic field from 210 mm ground-based magnetometers during quiet and active magnetospheric conditions. We search through 10 yr of these data to find events that qualify as quiet intervals, defined by Kp ≤ 1 for 1440 consecutive minutes. Similarly, active intervals require Kp ≥ 4 for 1440 consecutive minutes. The total for quiet intervals is ~ 4.3 x 106 and 2 x 108 min for active data points. With this large number of data we characterize changes in the nonlinear statistics of the geomagnetic field via measurements of a fractal scaling. A clear difference in statistical behavior during quiet and active intervals is implied through analysis of the scaling exponents; active intervals generally have larger values of scaling exponents. This suggests that although 210 mm data appear monofractal on shorter timescales, the scaling changes, with overall variability are more likely described as a multifractional Brownian motion. We also find that low latitudes have scaling exponents that are consistently larger than for high latitudes.

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