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International Geomagnetic Reference Field--2000 总被引：20，自引：0，他引：20
M. Mandea 《Pure and Applied Geophysics》2000,157(10):1797-1802
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We employ annually averaged solar and geomagnetic activity indices for the period 1960??C?2001 to analyze the relationship between different measures of solar activity as well as the relationship between solar activity and various aspects of geomagnetic activity. In particular, to quantify the solar activity we use the sunspot number R s, group sunspot number R g, cumulative sunspot area Cum, solar radio flux F10.7, and interplanetary magnetic field strength IMF. For the geomagnetic activity we employ global indices Ap, Dst and Dcx, as well as the regional geomagnetic index RES, specifically estimated for the European region. In the paper we present the relative evolution of these indices and quantify the correlations between them. Variations have been found in: i) time lag between the solar and geomagnetic indices; ii) relative amplitude of the geomagnetic and solar activity peaks; iii) dual-peak distribution in some of solar and geomagnetic indices. The behavior of geomagnetic indices is correlated the best with IMF variations. Interestingly, among geomagnetic indices, RES shows the highest degree of correlation with solar indices. 相似文献
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We analyze minimum and maximum daily temperature records from weather stations situated in the Canadian Arctic area and investigate scaling properties and their change over time. Detrended fluctuation analysis is applied to the entire available records, as well as to successive non-overlapping temporal windows. Scaling is found for intervals of 1–2?months to 5–8?years, with most exponents in the range 0.70?±?0.05. Exponents are subject to temporal change that is found significant when compared with 95?% confidence intervals. Patterns of change are shared by groups of stations in spite of the distances separating their locations. Defining regions characterized by similar patterns of change may be possible, but such a classification should not be expected to be constant: region boundaries shift over time. 相似文献
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Many Earth system processes generate magnetic fields, either primary magnetic fields or in response to other magnetic fields. The largest of these magnetic fields is due to the dynamo in the Earth’s core, and can be approximated by a geocentric axial dipole that has decayed by nearly 10% during the last 150 years. This is an order of magnitude faster than its natural decay time, a reflection of the growth of patches of reverse flux at the core–mantle boundary. The velocity of the North magnetic pole reached some 40 km/yr in 2001. This velocity is the highest recorded so far in the last two centuries. The second largest magnetic field in the solid Earth is caused by induced and remanent magnetization within the crust. Controlled in part by the thermo-mechanical properties of the crust, these fields contain signatures of tectonic processes currently active, and those active in the distant past. Recent work has included an estimate of the surface heat flux under the Antarctic ice cap. In order to understand the recent changes in the Earth’s magnetic field, new high-quality measurements are needed to continue those being made by Ørsted (launched in 1999), CHAMP and the Ørsted-2 experiment onboard SAC-C (both launched in 2000). The present paper is motivated by the advent of space surveys of the geomagnetic field, and illustrates how our way of observing, modeling, and interpreting the Earth’s magnetic field has changed in recent years due to the new magnetic satellite measurements. 相似文献
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Fractal dynamics of geomagnetic storms 总被引：1，自引：1，他引：0
Naïma Zaourar Mohamed Hamoudi Matthias Holschneider Mioara Mandea 《Arabian Journal of Geosciences》2013,6(6):1693-1702
We explore fluctuations of the horizontal component of the Earth’s magnetic field to identify scaling behaviour of the temporal variability in geomagnetic data recorded by the Intermagnet observatories during the solar cycle 23 (years 1996 to 2005). In this work, we use the remarkable ability of scaling wavelet exponents to highlight the singularities associated with discontinuities present in the magnetograms obtained at two magnetic observatories for six intense magnetic storms, including the sudden storm commencements of 14 July 2000, 29–31 October and 20–21 November 2003. In the active intervals that occurred during geomagnetic storms, we observe a rapid and unidirectional change in the spectral scaling exponent at the time of storm onset. The corresponding fractal features suggest that the dynamics of the whole time series is similar to that of a fractional Brownian motion. Our findings point to an evident relatively sudden change related to the emergence of persistency of the fractal power exponent fluctuations precedes an intense magnetic storm. These first results could be useful in the framework of extreme events prediction studies. 相似文献
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A new proposal for spherical cap harmonic modelling 总被引：4，自引：0，他引：4
E. Thébault J. J. Schott M. Mandea J. P. Hoffbeck 《Geophysical Journal International》2004,159(1):83-103