37 research outputs found
Fluctuations in the Alpha-Effect and Grand Solar Minima
Parameters of a special kind of \alpha-effect known in dynamo theory as the
Babcock-Leighton mechanism are estimated using the data of sunspot catalogs.
The estimates evidence the presence of the Babcock-Leighton \alpha-effect on
the Sun. Fluctuations of the \alpha-effect are also estimated. The fluctuation
amplitude appreciably exceeds the mean value, and the characteristic time for
the fluctuations is comparable to the period of the solar rotation.
Fluctuations with the parameters found are included in a numerical model for
the solar dynamo. Computations show irregular changes in the amplitudes of the
magnetic cycles on time scales of centuries and millennia. The calculated
statistical characteristics of the grand solar minima and maxima agree with the
data on solar activity over the Holocene.Comment: To appear in Astronomy Reports, 20 pages, 9 figure
Current status of the temperature and humidity regime of the troposphere in the Siberian sector in different circulation periods
The paper studies the long-term dynamics of air temperature and relative humidity anomaly indices in the surface layer and at different levels of the troposphere in Siberia and neighboring regions (European and Far Eastern sectors). As the main cause of the observed variations in climatic parameters we considered circulation factors, which were taken into account using the typification of macrocirculation processes proposed by B.L. Dzerdzeevsky. Seasonal differences were revealed in the distribution of anomaly indices and the area occupied by anomalies of different signs of annual and monthly mean temperature and relative air humidity, which are most pronounced during circulation periods of increased duration of meridional northern processes in the Siberian sector and in the Northern Hemisphere as a whole. The highest rates of change in the temperature regime in the Siberian sector over recent decades have been observed at the level of the isobaric surface AT–700 hPa (3 km), which affects the advective-dynamic factors of surface cyclo- and frontogenesis, as well as the processes of cloud formation and precipitation. In general, an increase in the heat content of the lower and middle troposphere and a decrease in the relative moisture content near the tropopause can be accompanied by an increase in the amount of the potential energy and convective instability energy reserves and can lead to an increase in climate risks in the Siberian sector
Economic fourth order three-stage method for solving systems of second order differential equations with special structure
An explicit embedded pair of methods for systems
of second order ordinary equations with special structure is
considered. Two-parametric families of methods of orders four
and three with automatic step-size control are constructed. The
numeric comparison to known embedded Runge–Kutta pairs of
the same order is hel
Sudden drop of fractal dimension of electromagnetic emissions recorded prior to significant earthquake
The variation of fractal dimension and entropy during a damage evolution
process, especially approaching critical failure, has been recently
investigated. A sudden drop of fractal dimension has been proposed as a
quantitative indicator of damage localization or a likely precursor of an
impending catastrophic failure. In this contribution, electromagnetic emissions
recorded prior to significant earthquake are analysed to investigate whether
they also present such sudden fractal dimension and entropy drops as the main
catastrophic event is approaching. The pre-earthquake electromagnetic time
series analysis results reveal a good agreement to the theoretically expected
ones indicating that the critical fracture is approaching
Does the Babcock--Leighton Mechanism Operate on the Sun?
The contribution of the Babcock-Leighton mechanism to the generation of the
Sun's poloidal magnetic field is estimated from sunspot data for three solar
cycles. Comparison of the derived quantities with the A-index of the
large-scale magnetic field suggests a positive answer to the question posed in
the title of this paper.Comment: 5 pages, 2 figures, to apper in Astronomy Letter
Solar dynamo model with nonlocal alpha-effect
The first results of the solar dynamo model that allows for the diamagnetic
effect of inhomogeneous turbulence and the nonlocal alpha-effect due to the
rise of magnetic loops are discussed. The nonlocal alpha-effect is not subject
to the catastrophic quenching related to the conservation of magnetic helicity.
Given the diamagnetic pumping, the magnetic fields are concentrated near the
base of the convection zone, although the distributed-type model covers the
entire thickness of the convection zone. The magnetic cycle period, the
equatorial symmetry of the field, its meridional drift, and the
polar-to-toroidal field ratio obtained in the model are in agreement with
observations. There is also some disagreement with observations pointing the
ways of improving the model.Comment: To appear in Astronomy Letters, 10 pages, 5 figure