NPG Nonlinear Processes in Geophysics NPG Nonlin. Processes Geophys. 1607-7946 Copernicus Publications Göttingen, Germany 10.5194/npg-21-347-2014 Latitudinal variation of stochastic properties of the geomagnetic field Wanliss J. A. 1 Shiokawa K. 2 Yumoto K. 3 Presbyterian College, 503 South Broad Street, Clinton, SC 29325, USA Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8601, Japan Space Environment Research Center, Kyushu University, 53 6-10-1 Hakozaki, Higashi-ku Fukuoka, 812-8581, Japan 03 03 2014 21 2 347 356 Copyright: © 2014 J. A. Wanliss et al. 2014 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://npg.copernicus.org/articles/21/347/2014/npg-21-347-2014.html The full text article is available as a PDF file from https://npg.copernicus.org/articles/21/347/2014/npg-21-347-2014.pdf

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 &le; 1 for 1440 consecutive minutes. Similarly, active intervals require Kp &ge; 4 for 1440 consecutive minutes. The total for quiet intervals is ~ 4.3 x 10<sup>6</sup> and 2 x 10<sup>8</sup> 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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