arXiv subjects

Irina A. Bilenko

Publications and source records attributed to Irina A. Bilenko.

6 recordsLinked to original sources

arXiv2026

Influence of local and global solar magnetic fields on medium-term forecasting of the number and parameters of coronal mass ejections

A study of cyclic variations in the number and parameters of coronal mass ejections (CMEs) in cycles 23-25 demonstrates differences in the behavior of strong and weak CMEs. Strong CMEs, unlike weak CMEs, follow the cyclic evolution of active regions. A method for separately predicting strong and weak CMEs is proposed. Based on global magnetic field (GMF) parameters, the timing of the minima of cycles 26 and 27 (CR~2375$\pm5$ and CR~2526$\pm5$), the duration of cycle 26 (151~CRs or 11.2838 years), and the periods of dominance of the GMF sectorial structure in cycles 25 and 26 ($\approx$CRs 2245-2355 and $\approx$CRs~2395-2546) were determined. Assuming similarities between cycles 26 and 20, a Wolf number forecast was made for cycle 26, based on which the number of strong CMEs in cycles 25 and 26 was predicted. Based on the ratio of weak to strong CMEs in cycle 23, a forecast of weak CMEs in cycles 25 and 26 was made. A comparison of the predicted and observed CME parameters in cycle 25 shows good agreement.

astro-ph.SR↗

arXiv2025

Solar Polar Field Reversals as the Result of the Global Magnetic field Meridional Flows

Based on data obtained from Wilcox Solar Observatiry the solar polar magnetic fields reversals in cycles 21\,--\,25 were considered. The results indicate that the polarity reversal occurs at the maximum of sunspot activity of each cycle, but the beginning, end, and duration of the reversals did not demonstrate any association with the Wolf numbers, which are characteristics of local magnetic fields. Moreover, during the periods of polarity reversal, the correlation between global magnetic field (GMF) parameters and Wolf numbers decreased and even moved into anti-correlation mode. The polar field reversals are determined by the GMF flows of positive- and negative-polarity magnetic fields, which cyclically migrate from one pole to the opposite pole. The new polarity magnetic fields are delivered to the poles by a certain flow, and then carried away by the same flow to the opposite pole. The increase in the polar magnetic field strength to its maximal values at the solar activity minimum and following decrees to the next cycle maximum coincides with the latitudinal changes in corresponding magnetic field flow. Formulas for calculating the meridional circulation of positive- and negative-polarity magnetic field flows were proposed. They allow predict the time of polarity reversals, and since polarity reversals occur at the maxima of cycles, then also the time of maxima of both the future and past cycles.

astro-ph.SR↗

arXiv2023

Meridional Circulations of the Solar Magnetic Fields of Different Strength

The meridional circulation of the solar magnetic fields in Solar Cycles 21-24 was considered. Data from both ground-based and space observatories were used. Three types of time-latitude distributions of photospheric magnetic fields and their meridional circulations were identified depending on the magnetic field intensity. (i) low-strength magnetic fields. They were distributed evenly across latitude and weakly depended on the magnetic fields of active regions and their cycle variation; (ii) medium-strength magnetic fields. For these fields a wave-like, pole-to-pole, antiphase meridional circulation with a period of approximately 22 years was revealed. The velocities of meridional flows were slower at the minima of solar activity, when they were at high latitudes in the opposite hemispheres, and maximal at the solar maxima, when the positive- and negative-polarity waves crossed the equator. The meridional circulation of these fields reflects the solar global magnetic field dynamics and determines the solar polar field reversal; (iii) high-strength (active region) magnetic fields. They were distributed symmetrically in the Northern and Southern hemispheres. Magnetic fields of both leading and following sunspot polarity migrated from high to low latitudes. The meridional-flow velocities of high-strength magnetic fields were higher at the rising and maxima phases than at the minima. Some of the high-latitude active region magnetic fields were captured by the second type meridional circulation flows and transported along with them to the appropriate pole. But the magnetic fields of active regions are not the main ones in the solar polar field reversal. The results indicate that high-strength magnetic fields were not the main source of weak ones.

astro-ph.SR↗

arXiv2019

Formation and evolution of coronal holes during the rising phase of cycle 23

Regularities of formation of coronal holes (CH) at the rising phase of cycle 23 are investigated. The period from 01.01.1997 to 01.03.2000 (Carrington rotations (CRs) 1918-2059) is considered in detail. The evolution of the global magnetic field (GMF) of the Sun from the zonal to the sectorial structure is analyzed. It is shown that the zonal structure is quasi-stable. The sum of zonal harmonics dominated up to CR 1941, although a stable four-sector structure of GMF was formed in 1932. In CRs 1941-1950 the contribution of the zonal and sectorial components becomes approximately equal and from CR 1950 the sectorial structure of GMF was dominated. Sectorial structure of GMF undergoing sharp changes from four-sector, at the beginning of growth of the sectorial harmonics (CR 1926), to the two-sector structure, then back to four-sector and then again to the two-sector structure. CHs clearly trace all evolutionary changes in the GMF. The structure of the polarity of the GMF uniquely determines the zones of photospheric magnetic fields where the CHs are formed.

astro-ph.SR↗

arXiv2018

Determination of the Coronal and Interplanetary Magnetic-Field Strength and Radial Profiles from the Large-Scale Photospheric Magnetic Fields

A new model has been proposed for magnetic field determination at different distances from the Sun during different solar cycle phases. The model depends on the observed large-scale non-polar photospheric magnetic fields and that measured at polar regions from 55N to 90N and from 55S to 90S,which are the visible manifestations of cyclic changes in the toroidal and poloidal components of the global magnetic field of the Sun. The modeled magnetic field is determined as the superposition of the non-polar and the polar photospheric magnetic field cycle variations. The agreement between the model predictions and magnetic fields derived from direct, in-situ, measurements at different distances from the Sun, obtained by different methods, and at different solar activity phases is quite satisfactory. From a comparison of the magnetic fields as observed and as calculated from the model at 1 AU, it should be concluded that the model magnetic-field variations adequately explains the major features of the IMF Bx component cycle evolution at the Earth's orbit. The model CR-averaged magnetic fields correlate with CR-averaged IMF Bx component at the Earth's orbit with a coefficient of 0.688, and for seven CR-averaged data the correlation reaches 0.808. The model magnetic-field radial profiles were compared with that of the already existing models. In addition, the decrease in the non-polar and polar photospheric magnetic fields has been revealed. Both magnetic fields during solar cycle maxima and that during minima phases decreased from Cycle 21 to Cycle 24. It means that both the toroidal and poloidal components and therefore, the solar global magnetic field decreased from Cycle 21 to Cycle 24.

astro-ph.SR↗

arXiv2018

Influence of the Solar Global Magnetic Field Structure Evolution on CMEs

The paper considers the influence of the solar global magnetic field structure (GMFS) cycle evolution on the occurrence rate and parameters of coronal mass ejections (CMEs) in cycles 23-24. It has been shown that over solar cycles, CMEs are not distributed randomly, but they are regulated by evolutionary changes in the GMFS. It is proposed, that the generation of magnetic Rossby waves in the solar tachocline results in the GMFS cycle changes. Each Rossby wave period favors a particular GMFS. It is proposed that the changes in wave periods result in the GMFS reorganization and consequently in CME location, occurrence rate, and parameter changes. The CME rate and parameters depend on the sharpness of the GMFS changes, the strength of the global magnetic field and the phase of a cycle.

astro-ph.SR↗