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A new magnetic index based on the external part of vertical geomagnetic variations

Ernst T., Jankowski J., Nowożyński K.

Acta Geophysica

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2010

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Vol. 58, no. 6

963-972

EN

Variations of geomagnetic components X, Y, and Z recorded in 19 Intermagnet European observatories in 2004 were analysed. The original data from all observatories were preliminarily processed. In the first step, periods longer than three hours were filtered out. In the second step, variations of vertical geomagnetic component Z were separated into external and internal parts. We introduced a non-dimensional index η defined as the square root of a ratio of the energy of the external part of the vertical component to that of the horizontal components. Maps of the surface distribution of a new magnetic index η for the area of Europe at selected time periods were created, and their time changes are presented. The time changes of η for selected observatories are also shown. Moreover, we discuss a very interesting phenomenon we discovered, that has never been described in geophysical literature. Namely, in the recordings of all the observatories we noticed the presence of very regular variations, observed almost exclusively in the vertical component Z, which is quite unusual. These regular variations occur in the form of sinusoidal "wave packets". The amplitudes of these variations do not depend on the geomagnetic latitude and appear in the records of all the observatories we analyzed. They occur in quiet days, which suggests that their source is in the ionosphere.

2

Geomagnetic variations and their time derivatives during geomagnetic storms at different levels of intensity

Watermann J., Gleisner H.

Acta Geophysica

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2009

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Vol. 57, no. 1

197-208

EN

The latitudinal distributions of horizontal geomagnetic variations, ΔH, and their time derivatives, ∂H/∂t, were analysed statistically over the three-year period 2003–2005. It appears that the amplitude distributions of horizontal geomagnetic variations and their time derivatives differ systematically between different geomagnetic latitudes and storm intensity levels. We show that the magnetic field variations observed at auroral and polar cap latitudes are under all geomagnetic storm levels comparable in amplitude (in a statistical sense) while they are smaller at subauroral latitudes. In contrast, their time derivatives are clearly the largest at auroral latitudes at all storm levels. These distributions determine in a general sense where and with which probability technological systems and operational procedures may be affected by geomagnetic storms. However, one observes in individual cases that the peak ∂H/∂t (the largest in all horizontal directions) is not necessarily the one which triggers a power system blackout.

3

Electrical conductivity anomalies in the crust and upper mantle of the Ukraine

Kulik S., Burakhovich T., Khazan Y.

Acta Geophysica Polonica

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2002

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Vol. 50, nr 4

547-565

EN

A wide range of tectonic structures exists on the territory of the Ukraine. Observations of geomagnetic induction vectors revealed anomalously high conductivity of many of them. A quasi-3D geoelectrical model of the Earth's crust and upper mantle of the Ukraine is based upon a thin-sheet approximation inside a regional cross-section of the electric conductivity. As the initial data we used induction vectors measured over the whole Ukrainian territory (about 2500 measurement points) for periods of geomagnetic variations ranging from 150 up to 2000 seconds. After removing the influence of the known distribution of the subsurface conductance (sediments), the residual vectors have been analyzed as being caused by the Earth's crust and upper mantle sources. The model demonstrates that values of the local conductance reduced to thin-sheets range from 0.5 to 20 kS in the Earth's crust and from 2 to 6 kS in the upper mantle. Both, the nature and the origin, of these high conductivity zones are different for different regions. Some possibilities including a contribution of the percolation process in two-phase media are discussed.