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The results of comparative analysis of the behavior of paleointensity and polarity (intervals between reversals) of the geomagnetic field for the last 167 Ma are presented. Similarities and differences in the behavior of these characteristics of the geomagnetic field are discussed. It is shown that bursts of paleointensity and long intervals between reversals occurred at high mean values of paleointensity in the Cretaceous and Paleogene. However, there are differences between the paleointensity behavior and the reversal regime: (1) the characteristic times of paleointensity variations are less than the characteristic times of the frequency of geomagnetic reversals, (2) the achievement of maximum values of paleointensity at the Cretaceous-Paleogene boundary and the termination of paleointensity bursts after the boundary of 45-40 Ma are not marked by explicit features in the geomagnetic polarity behavior. [ABSTRACT FROM AUTHOR]

The available paleomagnetic data on the Verkhnyaya Lena Group from different areas of the southern Siberian Platform are revised. The group rests unconformably upon the Lower Cambrian strata and is overlain by Lower Ordovician rocks, which determines conditionally the age of its red-colored deposits. Paleomagnetic correlation of composite sections through the region using defined zones of normal and reversed magnetic polarity serves as a basis for development of the magnetostratigraphic scale for the Verkhnyaya Lena Group. The scale includes nine magnetic zones, which play the role of markers; seven of them are traceable in all the examined sections of the southern Siberian Platform. By the distribution of zones with normal (N) and reversed (R) polarity, the magnetostratigraphic scale is subdivided into three parts. Its lower part is represented by reversed polarity, which is characteristic of the second half of the Lower Cambrian. The middle part is characterized by frequently alternating zones with normal and reversed polarity corresponding to the Middle Cambrian. The upper part of the scale corresponds to the interval of reversed polarity characteristic of the Upper Cambrian and Lower Ordovician. The Middle-Upper Cambrian boundary is located near the last N-R reversal of the geomagnetic field in the Cambrian. The magnetostratigraphic scale includes nine orthozones united into three superzones, which are attributed to two hyperzones of magnetic polarity. [ABSTRACT FROM AUTHOR]

The distribution of the paleointensities and the lengths of geomagnetic polarity intervals (time intervals between the successive reversals of the Earth's magnetic field) corresponding to the different geological epochs was studied. It was found that the stochastic series of paleointensities in most cases are best approximated by the power-law function. The exponents of the power-law distributions vary depending on the intervals of the geological time that accommodate the analyzed paleomagnetic data. The distributions of the lengths of polarity intervals are approximated by the exponential function. The exponents varied depending also on the intervals of the geological time. The analysis shows that the most significant changes in the behavior of paleointensity occurred in the Paleogene near the Paleocene-Eocene boundary. Based on the analysis of the paleomagnetic data, it is hypothesized that turbulence of the magnetoactive medium played an important role in the generation of the Earth's magnetic field. The turbulence of the magnetoactive medium increased in the Cretaceous compared to the Jurassic and Paleogene. [ABSTRACT FROM AUTHOR]

The article discusses geomagnetic reversal and the consequences that may occur due to this problem. Topics discussed include relationship of magnetic field and geomagnetic reversal, geomagnetic field polarity, and magnetic field excursions. Also discussed is the analysis of Late Cretaceous–Cenozoic (C-sequence).

This paper describes a new method for reconstructing the polarity of the interplanetary magnetic field. The technique is based on the Svalgaard-Mansurov effect. We ause geomagnetic data of high-latitude stations with a long observation period, including the presatellite era. This method is designed to improve the quality and accuracy of reconstructed polarity, complementing the results of previous methods of Svalgaard (1975) and Vennerström et al. (2001). For the large presatellite period from 1926, the accuracy of the method is estimated to be around 89% of overlaps with the interplanetary magnetic field polarity determined from satellite data. [ABSTRACT FROM AUTHOR]

This review addresses possible biospheric effects of geomagnetic polarity transitions. During a transition the magnetic field at the surface of the Earth decreases to about 10% of its current value. If the geomagnetic field is a shield against energetic particles of solar or cosmic origin then biospheric effects can be expected. We review the early speculations on the problem and discuss in more detail its current status. We conclude that no clear picture of a geomagnetic link, a causal relation between secular magnetic field variations and the evolution of life on our planet can be drawn. [ABSTRACT FROM AUTHOR]

Recent advances in the study of geomagnetic field reversals are reviewed. These include studies of the transitional field during the last geomagnetic reversal and the last geomagnetic excursion based on paleomagnetic observations, and analysis of reversals in self-consistent 3D numerical dynamo simulations. Field models inferred from observations estimate reversal duration in the range of 1-10 kyr (depending on site location). The transitional fields during both the Matuyama/Brunhes reversal and the Laschamp excursion are characterized by low-latitude reversed flux formation and subsequent poleward migration. During both events the dipole as well as the non-dipole field energies decrease. However, while the non-dipole energy dominates the dipole energy for a period of 2 kyr in the reversal, the non-dipole energy merely exceeds the dipole energy for a very brief period during the excursion. Numerical dynamo simulations show that stronger convection, slower rotation, and lower electrical conductivity provide more favorable conditions for reversals. A non-dimensional number that depends on the typical length scale of the flow and represents the relative importance of inertial effects, termed the local Rossby number, seems to determine whether a dynamo will reverse or not. Stable polarity periods in numerical dynamos may last about 1 Myr, whereas reversals may last about 10 kyr. Numerical dynamo reversals often involve prolonged dipole collapse followed by shorter directional instability of the dipole axis, with advective processes governing the field variation. Magnetic upwellings from the equatorial inner-core boundary that produce reversed flux patches at low-latitudes of the core-mantle boundary could be significant in triggering reversals. Inferences from the observational and modeling sides are compared. We summarize with an outlook on some open questions and future prospects. [ABSTRACT FROM AUTHOR]

The asymmetry of the magnetic field of the Sun and its manifestation in the interplanetary magnetic field (IMF) are studied. The dominant magnetic polarity of the radial component of the IMF alternates from cycle to cycle, but with an overall systematic dominance of polarity directed toward the Sun. The global asymmetry is also manifest in the component of the IMF perpendicular to the plane of the solar equator. The dominance of positive values of B z together with an appreciable linear trend in the cumulative sum of this quantity is interpreted as a manifestation of a relic solar magnetic field. The strength of this relic magnetic field near the Earth is estimated to be 0.048 ± 0.015 nT, based on the growth of the linear component of the cumulative sum of B z . Time intervals, in which negative values of the B z component of the IMF dominate and enhanced geomagnetic activity is observed, are identified. Our analysis of solar and heliospheric magnetic fields in an integrated representation has enabled us to compare various types of measurements and estimate their stability. [ABSTRACT FROM AUTHOR]