SPECTRAL ANALYSIS AND FORECASTING OF THE 25TH SOLAR CYCLES

In the present work, we propose an extrapolation method, developed on the basis of spectral analysis, digital filtering, and the principle of demodulation of a complex signal, for predicting the beginning of cycle 25 of solar activity. The Wolf number and other measured characteristics of solar activity have a very complex spectral composition. The Sun, by the nature of its radiation, contributes a significant stochastic component to the observational data. The experimental data are known only up to the present, and the prediction is about bridging the gap in our data set. Mathematically, the prediction problem boils down to extrapolation of discontinuous functions, which leads to a Gibbs phenomenon that occurs at the point of discontinuity and makes prediction into the future impossible. To overcome this discontinuity, additional physical models describing a continuous process are most often used. This paper uses only the Wolf series of numbers from 1818 to 2020. The authors developed an original forecasting technique using Fourier series, digital filtering and representation of the complex process as modulated and subsequent demodulation. As a result of decomposing the complex signal by Fourier series into separate components, the spectral ranges characteristic of the Wolf number were singled out. Taylor's series was used for construction of prediction or extrapolation algorithms. The extraction of spectral ranges, characteristic for the investigated process, is carried out by means of sequential digital filtering methods and information compression in accordance with the cut-off frequency of the digital filter. For example, when selecting eleven-year cycles of solar activity, we have to compress the information by a factor of 160. With such a processing scheme, the forecasting starts with the ultralow-frequency component with a period of more than 11 years, successively moving to the ranges of higher frequencies. The use of spectral analysis and Chebyshev filtering showed the possibility to predict the low-frequency component for the full cycle period. The eleven-year component forecast obtained by the authors is in good agreement with the data of the Brussels Royal Center.

The mean tilt of sunspot bipolar regions: theory, simulations and comparison with observations

ABSTRACT A theory of the mean tilt of sunspot bipolar regions (the angle between a line connecting the leading and following sunspots and the solar equator) is developed. A mechanism of formation of the mean tilt is related to the effect of the Coriolis force on meso-scale motions of super-granular convection and large-scale meridional circulation. The balance between the Coriolis force and the Lorentz force (the magnetic tension) determines an additional contribution caused by the large-scale magnetic field to the mean tilt of the sunspot bipolar regions at low latitudes. The latitudinal dependence of the solar differential rotation affects the mean tilt, which can explain deviations from Joy’s law for the sunspot bipolar regions at high latitudes. The theoretical results obtained and the results from numerical simulations based on the non-linear mean-field dynamo theory, which takes into account conservation of the total magnetic helicity and the budget equation for the evolution of the Wolf number density, are in agreement with observational data of the mean tilt of sunspot bipolar regions over individual solar cycles 15–24.

Variations in the length of Scots pine (Pinus sylvestris L.) needles under the influence of climatic factors and solar activity in different conditions of northern taiga

The aim of the study was to assess the influence of climatic factors on the growth of pine needles in different conditions of the water regime of soil. Studies were conducted in lichen pine forests, cowberry pine forests, blueberry pine forests, shrub-sphagnum pine forest and pine on swamp in the Arkhangelsk forestry regions (northern taiga). The needle length is influenced by solar activity (the Wolf number). The effect of solar activity on increasing the needle length is greatest in optimal growing conditions. In northern taiga conditions, air temperature is the main climatic factor affecting the growth of needles. In the blueberry, cowberry and lichen pine forests, an inverse high correlation of the needle length with the night air temperature of August of the current year was revealed. The pine on swamp revealed a high correlation between the needle length and the air temperature at the end of July of the current year of needle development. In the year preceding the needle development, a high inverse correlation was found between the needle length and the temperature of mid-September in the cowberry and blueberry pine forests. In the current year, high correlations of the lengths of needles and precipitation were observed in extreme growing conditions.<br />

Nonlinear mean-field dynamo and prediction of solar activity

We apply a nonlinear mean-field dynamo model which includes a budget equation for the dynamics of Wolf numbers to predict solar activity. This dynamo model takes into account the algebraic and dynamic nonlinearities of the$\unicode[STIX]{x1D6FC}$effect, where the equation for the dynamic nonlinearity is derived from the conservation law for the magnetic helicity. The budget equation for the evolution of the Wolf number is based on a formation mechanism of sunspots related to the negative effective magnetic pressure instability. This instability redistributes the magnetic flux produced by the mean-field dynamo. To predict solar activity on the time scale of one month we use a method based on a combination of the numerical solution of the nonlinear mean-field dynamo equations and the artificial neural network. A comparison of the results of the prediction of the solar activity with the observed Wolf numbers demonstrates a good agreement between the forecast and observations.

An ionospheric index suitable for estimating the degree of ionospheric perturbations

Space weather can strongly affect trans-ionospheric radio signals depending on the used frequency. In order to assess the strength of a space weather event from its origin at the sun towards its impact on the ionosphere a number of physical quantities need to be derived from scientific measurements. These are for example the Wolf number sunspot index, the solar flux density F10.7, measurements of the interplanetary magnetic field, the proton density, the solar wind speed, the dynamical pressure, the geomagnetic indices Auroral Electrojet, Kp, Ap and Dst as well as the Total Electron Content (TEC), the Rate of TEC, the scintillation indices S4 and σ(ϕ) and the Along-Arc TEC Rate index index. All these quantities provide in combination with an additional classification an orientation in a physical complex environment. Hence, they are used for brief communication of a simplified but appropriate space situation awareness. However, space weather driven ionospheric phenomena can affect many customers in the communication and navigation domain, which are still served inadequately by the existing indices. We present a new robust index, that is able to properly characterize temporal and spatial ionospheric variations of small to medium scales. The proposed ionospheric disturbance index can overcome several drawbacks of other ionospheric measures and might be suitable as potential driver for an ionospheric space weather scale.

Evaluation of significance of melatonin and some atmospheric and heliogeophysical factors for patients with acute coronary syndrome

Introduction. Changes in melatonin (MT) production affected by earth magnetic field (EMF) were documented, including but not limited to patients with cardiovascular diseases. Thus far, the connection between MT content and atmospheric and heliogeophysical factors with regard to acute coronary syndrome (ACS) patients has not been thoroughly studied and the existing data are controversial. Material and methods. The levels of MT metabolite 6-hydroxymelatonin were measured in urine at night (MTn) and day (MTd) time in 114 ACS and 26 stable angina (SA) patients on days 1-3 of hospital stay. Results. Significant inverse correlation between MTn content and EMF H and D-components (H, D) of EMF was found in ACS patients as well as direct correlation between the MTn levels and solar radiation flux density at a wavelength of 10.7 cm (F-10.7) and the number of sun spots (the Wolf number - W). Significant direct correlation was shown between EMF D-component value, Kp- and Ap- geomagnetic activity indices in ACS patients developing cardiovascular complications. For ACS patients, the risk of development of cardiovascular complications was 1,62 and 1,15 times greater at high Kp- and Ap-indices respectively. Conclusion. Direct connection between MTn level and solar activity factors was observed in ACS patients together with inverse correlation with geomagnetic activity which confirms the influence of heliogeophysical factors on MT production. The risk of developing cardiovascular complications increases at higher Kp-and Ap- indices which proves the effect of heliogeophysical factors on the clinical course of cardiovascular pathology. The MTn content was shown to decrease in winter in these patients.

Influence of Solar Physics Factors on the Spring Growth of Phytoplankton in Reservoir

The article gives the results of retrospective statistical analysis, which justify the presence of statistical dependencies between the dates of the beginning and the peak values of the spring phytoplankton bloom in the Uchinsk reservoir and the intensity of total solar radiation in the range of photosynthetically active radiation (PAR), as well as the value of the integral indices of the activity of the Sun (Wolf number), in the period preceding of phytoplankton bloom. It is found, that the greater the magnitude of the fluxes of solar radiation in the PAR range will get the surface of the reservoir for 28 days of February this year, the later will be observed peaks of the spring phytoplankton bloom.A positive correlation between the parameters of the light regime (the sum of PAR) and the period of the onset of the algae “bloom” in the reservoir is apparently related to the photoinhibition of phytoplankton development directly under the ice, which leads to a later development of the spring “bloom”.The verification of the obtained regression equation showed a good correspondence of actual and calculated dates of spring “bloom” for a ten-year period. A negative correlation was found between the values of Wolf numbers (in February and the average annual values of the current year) and the dates of the spring peaks of phytoplankton bloom, which can be explained by the stimulating nature of the effect of the intensity of natural magnetic fields on the development of phytoplankton.The results of the investigations are of undoubted interest for the analysis of the influence of the light factor and the integral activity of the Sun on the seasonal dynamics of phytoplankton in the reservoir, as well as for an accurate forecast of the onset of spring phytoplankton bloom in drinking-water reservoirs in planning water treatment and water treatment activities.

Statistical Effects in the Solar Activity Cycles during AD 1823–1996

General statistical properties of solar activity cycles during the period AD 1823–1996—including the Gnevyshev-Ohl and Waldmeier effects as well as an amplitude-period effect—were analyzed using Wolf number, group sunspot number, and extended total sunspot area series. It was found out that the Gnevyshev-Ohl effect GO2 (the positive correlation between intensity of the even cycles 2N and intensity of the odd cycles 2N+1) and the Waldmeier effect W2 (the anticorrelation between rise times of sunspot cycles and their amplitudes) are the most universal and robust features of the solar cycle. Other statistical relations were found appreciably sensitive to the selection of solar index, the interval of analysis, and the way of the cycle feature determination.