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In solar activity, in addition to the 11-year Schwabe cycle, there are also shorter-period oscillations in the range from 27 days to 11 years, which are called mid-term oscillations. In our study, we identify quasi-6-year oscillations in solar activity expressed by the sunspot number SN using wavelet analysis and investigate the characteristics of these variations during 1750–2020. The analysis shows that the ~6-year cycle in SN is a real independent oscillation. A similar quasi-6-year periodicity has been found in the monthly mean records of geomagnetic field components at the Sitka and Honolulu observatories during 1910–2020. It was found that the variations of the geomagnetic field in the range of 5–6-year periods can be caused by the effect of variations in solar activity in the same frequency range. In addition, in the SN series and geomagnetic field variations, a quasi-biennial cycle is well observed, the amplitude of which in some time intervals exceeds the amplitude of the cycle with a period of 5–6 years. [ABSTRACT FROM AUTHOR]

We calculated variations in the cosmic ray geomagnetic cutoff rigidity ΔRef during a complex two-stage magnetic storm on November 9–10, 2004, using calculations of particle trajectories in the model magnetic field of the magnetosphere. The response of ΔRef to changes in solar wind and magnetosphere parameters reflects the nonsmooth two-stage evolution of this storm. It is found that the curve of changing values that ΔRef take as a function of the studied parameters during the main phases of each stage of the storm does not coincide with the curve during the recovery phases, which is a sign of hysteresis. As a result, two hysteresis loops are formed, one for each stage of the storm of November 9–10, 2004. The ambiguous dependence of ΔRef values on the studied parameters, which change cyclically during the development of magnetospheric current systems and their subsequent relaxation, is responsible for the formation of the loops. The configuration of two loops similar to those characteristic of dielectric hysteresis seems to be related to the abrupt change from Bz > 0 to Bz < 0, which delimits the stages of the studied storm. [ABSTRACT FROM AUTHOR]

One of the most significant features of solar activity is its variability in a wide range of periods with the dominance of the 11-year cycle or the Schwabe cycle. In this article, a wavelet analysis of solar activity data for 1000–1700 obtained using the number of auroras taking into account the contribution of the geomagnetic field taken into account is performed. The results show the stable presence of an 11-year cycle throughout 1000–1700. It is found that there is a systematic increase in the Schwabe cycle length in 1000–1350, after which its decrease is observed. At the same time, the length of the solar cycle increases during the Oort (13 years), Wolf (14 years), and Spörer (14–15 years) grand minima. It is established that the correlation between the amplitude and length of the solar cycle was preserved over the entire time interval of 1000–1700, but its sign changed. It is also found that the correlation between the amplitude of the cycle and the length of the previous cycle is stronger than the correlation between the amplitude and the length of the same cycle. This result is similar to what is known previously for instrumental series. However, we show that this pattern persists over a much longer time interval, and it does not depend on the sign of the correlation. The article also provides indications of the existence of solar activity variations in 1000–1550 with a period of 30–40 years. [ABSTRACT FROM AUTHOR]

Using wavelet analysis, a study was made of variations in the length of the solar cycle and their characteristic features in 1700–2020. In addition to the stable 11-year component, in the spectrum of solar activity there are three components of the Gleissberg cycle: a ~115-year component is visible over the entire time interval and a ~60-year component occurs until 1875. The classical branch with a period of 88 years is separated in 1775–1910s. In the wavelet spectrum, the Dalton minimum is characterized by a sharp increase in the length of the 11-year component against the background of a decrease in amplitude in ~1800, and also by the fact that all three branches of the Gleissberg cycle are practically symphasic, and their amplitudes are close to the maximum. A model is constructed in which the period of the 11-year harmonic oscillation is modulated by three branches of the Gleissberg cycle. It is found that such a model of frequency modulation describes the general evolution of the spectrum and its main features well, in particular, the Dalton minimum. [ABSTRACT FROM AUTHOR]

Using wavelet analysis, a study was made of variations in the length of the solar cycle and their characteristic features in 1700–2020. In addition to the stable 11-year component, in the spectrum of solar activity there are three components of the Gleissberg cycle: a ~115-year component is visible over the entire time interval and a ~60-year component occurs until 1875. The classical branch with a period of 88 years is separated in 1775–1910s. In the wavelet spectrum, the Dalton minimum is characterized by a sharp increase in the length of the 11-year component against the background of a decrease in amplitude in ~1800, and also by the fact that all three branches of the Gleissberg cycle are practically symphasic, and their amplitudes are close to the maximum. A model is constructed in which the period of the 11-year harmonic oscillation is modulated by three branches of the Gleissberg cycle. It is found that such a model of frequency modulation describes the general evolution of the spectrum and its main features well, in particular, the Dalton minimum. [ABSTRACT FROM AUTHOR]

Variations in the cutoff rigidities of cosmic rays (ΔR) depending on the parameters of the solar wind, the interplanetary magnetic field (IMF), and geomagnetic activity were studied at different phases of the strong magnetic storm on May 15, 2005. We found that the trajectories ΔR, i.e., the successive values that ΔR takes depending on the parameters under study during the main phase of the storm did not coincide with the trajectories in the recovery phase, which led to the formation of hysteresis loops. The clearest hysteresis loops are formed for the relationship between ΔR and the Bz component of the IMF, the density and pressure of the solar wind, and the Dst index of geomagnetic activity. The area of the hysteresis loops increases with the latitude of the cosmic ray observation station. [ABSTRACT FROM AUTHOR]

The wavelet analysis was used to study the spectral composition of the sunspot numbers SN during 1700–2021. In addition to the dominant 11-year component, two powerful components of the Gleissberg cycle can be traced in the spectrum: before 1880, a branch with a period of ~60 years; from 1850 a branch of ~115 years is found. It is found that the series of lengths and amplitudes of the solar cycle as a whole are inversely related (correlation coefficient k = –0.5–0.63). The interval between the series at which the maximum anticorrelation is reached depends on time. In the 18th and early 19th centuries, the lag was equal to one cycle, in the 19th century it was two cycles, and from 1950 to our time the lag decreased to 2 years. Quasi-periodic structures, which are typical for long periods of low solar activity, have been identified. Such a spectral feature in ~1800 (Dalton minimum) was caused by the influence of the 60-year branch, while the one that has been forming since the beginning of the 21st century is due to the weaker influence of the circa-centenary branch. Therefore, it should be expected that the next solar cycles will be higher and shorter than during the period of the Dalton minimum. It has been shown that solar cycle length variations for the last 321 years can be described within the framework of the model, which is an 11-year oscillation that is subject to frequency modulation by the branches of the Gleisberg cycle (60 and 115 years) with time-varying influences of the modulator. [ABSTRACT FROM AUTHOR]

We have studied the features of the latitudinal behavior of geomagnetic thresholds of cosmic rays R, as well as their sensitivity to the interplanetary medium and magnetospheric parameters during three phases of the magnetic storm on September 7–8, 2017, in the initial, main, and recovery phases. For this purpose, values of R were calculated in two different ways—by the method of spectrographic global survey (Rsgs) and by the method of tracing the trajectories of cosmic-ray (CR) particles in the model magnetic field (Ref). The maximum lowering of thresholds is observed at the storm maximum (Dst = –142 nT), reaching the values of ΔRsgs = –0.52 GV and ΔRef = –0.66 GV. The curve of ΔRsgs variations, depending on the observation station (latitude) cutoff rigidity, assumes a classical form with a maximum dropping the thresholds at midlatitudinal stations. ΔR correlates most strongly with the Dst index, which indicates that the ring current plays a main part in the dependence of variations of CR cutoff rigidities. The significant influence of solar-wind velocity V and interplanetary magnetic field (IMF) parameters on ΔRsgs and ΔRef is also seen. In the main phase, ΔRef depends on B and Bz of the IMF, and ΔRsgs depends on B and By. For ΔRsgs, the correlation with electromagnetic parameters varies, depending on the observation station, in a regular manner. There is no such tendency for ΔRef. [ABSTRACT FROM AUTHOR]

Of the solar-activity cycles with a period exceeding 22 years, the secular cycle, known as the Gleissberg cycle, attracts the most attention from researchers. In this paper, using the Fourier and wavelet analysis methods, we study the cyclicity of solar activity expressed by the sunspot number SN reconstructed from different sources (the length of the series is up to ~12 000 years) in the range of periods of the Gleissberg cycle. It was found that the Gleissberg cycle consists of three distinguished branches with average periods of 60, 88, and 140 years. The nature of the amplitude variation of all three branches is identical, which indicates that they are part of one quasi-periodic process. The analysis showed that the 88-year cycle is the main cycle. Its source is the solar dynamo. The 60- and 140-year cycles are the result of frequency modulation of the main cycle by a process with a period of 224 years (Suess cycle). A model that confirms and explains this result has been developed. The Suess cycle, which is a frequency modulator of the Gleissberg cycle, most likely has an extrasolar origin. Our results do not support the hypothesis of a chaotic Sun, which is indicative of a more regular, quasi-periodic behavior of the solar dynamo. [ABSTRACT FROM AUTHOR]

The ability of cosmic rays to penetrate the magnetosphere is characterized by the rigidity of the geomagnetic cutoff R, i.e., the stiffness below which the particle flux is cutoff due to magnetic screening. During a magnetic storm, the topology of the magnetic field changes; this causes variations in the cutoff rigidity ΔR. The dependence of ΔReff (which is calculated from the tracing of the trajectories of cosmic ray particles in a model magnetospheric field) on the parameters of the solar wind, the interplanetary magnetic field, and the magnetosphere during different phases of the strong magnetic storm on November 7–8, 2004 is considered. It is found that the trajectory of ΔReff, i.e., the successive ΔReff values with respect to the studied parameters, does not coincide with the trajectory in the recovery phase during the main phase: hysteresis loops form. Narrow hysteresis loops were obtained to relate ΔReff to the geomagnetic index Dst and the solar wind velocity, while wide loops were obtained to relate it to the electromagnetic parameters. The shape of the hysteresis loops are indicative of a dependence on the latitude of observation: as the latitude increases, the loop area also increases for all studied parameters. [ABSTRACT FROM AUTHOR]

We examined cycles of solar activity reconstructed based on the number of auroras observed at the middle and low latitudes in 1000–1700. We used a wavelet analysis method. Variations in the Earth's magnetic moment influence the propagation of cosmic particles that cause auroras. We took this influence into account when reconstructing solar activity based on variations in the number of auroras. The analysis was carried out for a combined series: the reconstructed series of sunspots SN (1000–1700) and the modern SN series (1700–2000). Two dominant components were found in the SN spectrum: the near-centennial Gleissberg cycle, which consists of two modes with periods of 60–80 and 90–140 years, and a nearly two-century Suess cycle. When the the contribution of the magnetic moment is taken into account, the amplitudes of the periods of the Gleissberg group in the SN spectrum increase as compared to the initial spectrum of the aurora number, and their intensity approaches the intensity of the Suess variation. Analysis of changes in the amplitudes and periods of all cycles showed the presence of long-wave modulation with a possible period ranging from 1300 to 1700 years. As for the Gleissberg cycles, a frequency modulation with a period of 216 years by the Suess cycle was also revealed. We believe that the ~200-year component has an extrasolar nature and may reflect the result of the duplication of the fundamental frequency (11 and 22-year cycles) on multiple modulator modes. [ABSTRACT FROM AUTHOR]

The correlations between variations in the geomagnetic cutoff rigidity of cosmic rays and the Dst and Kp geomagnetic indices and solar-wind and IMF parameters are calculated for the three phases of the magnetic storm of November 20–21, 2003: before the storm and during its main and recovery phases. The correlations are the strongest between variations in the cutoff rigidity and the Dst index during all stages. A significant correlation was recorded with the By component of IMF and the field magnitude B; the correlation with By dominated during the main phase, and the correlation with B was dominant during the recovery phase. There is also a high correlation with the dynamic parameters of solar activity during the main phase, especially with the solar-wind speed. As far as we know, hysteresis phenomena have been discovered for the first time in the relationship between the cosmic-ray cutoff rigidities and the parameters of the helio- and magnetosphere on the scale of the magnetic storm (with Moscow station as an example). Loop-like patterns formed, because the trajectories of variations in the cutoff rigidities versus the studied parameters during storm intensification (development of current systems) did not coincide with the trajectories during the recovery phase (decay of current systems). The correlations of the cutoff rigidities with Dst and Kp indices were characterized by a narrow hysteresis loop, and their correlations with the IMF parameters were characterized by a wide hysteresis loop. The hysteresis loops for the relationship between the cutoff rigidities and solar-wind density and pressure were disordered. [ABSTRACT FROM AUTHOR]

A new reconstruction of the number of sunspots (SN) in 1000–1700, along with possible errors, has been obtained based on an analysis of auroral observations at middle and low latitudes and data on the Earth's magnetic field at that time. The intensity and configuration of the main magnetic field of the Earth affect the penetration of the Earth's magnetosphere and atmosphere by aurora-induced, charged, solar-wind particles. Our reconstruction differs from other authors in that we have taken into account this effect on the frequency of auroras. The time variation of the reconstructed SN shows the previously known minima of Oort, Wolf, Spörer, and Maunder. The SN values for 1100–1150 (medieval maximum) are comparable to those observed in the second half of the XX century during the current period of high solar activity. It is shown that SN decreases by approximately two times during the Maunder minimum in comparison with the previous period, but it can reach SN ≈ 40 in some years. Bifurcation and degeneration of the 11-year cycle occurs at the beginning of the Maunder minimum. It can be associated with the difference in solar dynamo modes. [ABSTRACT FROM AUTHOR]

The correlation of the variations in geomagnetic cutoff rigidity of cosmic rays ΔR with the interplanetary medium parameters and geomagnetic activity indices Dst and Kp was calculated for different phases of the superstorm on November 7–8, 2004. The strongest correlation was observed between the cutoff rigidity and Dst at all stages of storm development (correlation coefficients k ≈ 0.70–0.98); some stable influence of the solar wind (SW) density N (k ≈ 0.50–0.80) should also be noted. The dependence of the cutoff-rigidity variation on all of the dynamic parameters of the SW is observed in the main storm phase and is especially strong for the density N and pressure P. The correlation between ΔR and V is negative in all phases, while the correlation of ΔR with N and P is positive during the main phase and negative in the recovery phase. The cutoff-rigidity variations showed no sensitivity to the Bz component of the interplanetary magnetic field (IMF), the azimuthal component By, or the IMF absolute value B before the storm or in its main phase. A significant correlation or anticorrelation of ΔR with B and all the IMF components is observed only in the recovery period. The specific response of the geomagnetic cutoff rigidity to the heliospheric and magnetospheric parameters at different phases of the magnetic storm is apparently determined by the different relative contributions of the magnetospheric global current systems during these periods. [ABSTRACT FROM AUTHOR]

The correlation between the variations of geomagnetic cutoff rigidity ΔR and interplanetary parameters and the Dst index of geomagnetic activity during one moderate and six strong storms of solar cycles 23 and 24 has been calculated. The ΔR values have been obtained with two methods: (1) the spectrographic global survey method (SGS), in which the determination of the cutoff rigidity RSGS is based on observational data from the neutron monitor network, and (2) a method in which the particle trajectories are calculated numerically in a model magnetic field of the magnetosphere to determine the cutoff rigidity Reff. In general, the results obtained by the two methods are in close agreement. The Dst index of geomagnetic activity has the greatest effect on ΔR, and the correlation increases with storm intensity. The sensitivity of ΔR to interplanetary parameters vary greatly for different storms. The most geoeffective interplanetary parameter is the solar-wind speed V. A significant anticorrelation of ΔR and V can be traced for almost all storms. The correlation of ΔRSGS with the Bz component of the interplanetary magnetic field is observed only for two storms, on November 7–14, 2003, and November 7–8, 2004, for which the absolute Bz value was very high (≈−50 nT). At the same time, there is a rather high correlation of ΔReff with Bz for most storms. The azimuthal component of the interplanetary field By and the solar-wind dynamic pressure P show almost no connection with ΔR. [ABSTRACT FROM AUTHOR]

In this work, geomagnetic cutoff rigidities are calculated in a model magnetosphere field on the world latitude–longitude 5° × 15° grid during the main phase of the magnetic storm of November 20, 2003. A decrease in geomagnetic thresholds (ΔR) by up to 1.8 GV as compared to thresholds in the main field is observed in the maximum of the geomagnetic storm at 2000 UT at middle and low latitudes. In the equatorial part, ΔR amounts to 0.5–0.6 GV. It has been found that the global distribution of drops in the cutoff rigidities exhibits a North–South asymmetry, as well as day–night asymmetry. This is expressed by the fact that the ΔR maximum in the daytime sector is observed at a latitude of ~40° N in the Northern Hemisphere and ~60° S in the Southern Hemisphere. Conversely, the ΔR maximum is observed in the nighttime sector at a latitude of ~55° N in the Northern Hemisphere and ~45° S in the Southern Hemisphere. Moreover, the maximum ΔR values in the Northern Hemisphere in the daytime sector are higher than in the nighttime sector; in the Southern Hemisphere, the maximum ΔR values in the daytime sector are lower than in the nighttime sector. The observed magnetospheric effects in the global distribution of ΔR seem to be caused by the dominant impact of the partial ring current that develops in the main storm phase. [ABSTRACT FROM AUTHOR]

Abstract: We estimate the contribution of the systematic component of the Earth's main magnetic field (MMF), i.e., the main dipole, to the secular variation in the midlatitude polar auroras based on the archived data. It is found that the main features of the variations in the magnetic moment (MM) of the main dipole in 1600-1909 are reflected in variations in the annual number of polar auroras N with the opposite sign (correlation coefficient of 0.6-0.8). A model of the dependence of the number of polar auroras N on the solar activity expressed in the Wolf number W and on the MM value is proposed. Taking into account the effect of the MM noticeably improves the properties of the N versus W dependence. It is found that the disagreement between the 11-year cycles of N and W observed in 1700-1775, as well as the minimum N in ~1760-1767 (Silverman minimum), are conditioned by MM variations in the corresponding periods of time. A rapid increase in the MM near 1800 significantly contributes to the steep decline in N during the Dalton minimum. During those historical periods in which the MM value was 1.5-2 times greater than in the 17th-19th centuries (according to the archeomagnetic data), the number of polar auroras could be conditioned not so much by the solar activity as by the screening effect of the MMF. [ABSTRACT FROM AUTHOR]

Abstract—: In situ data on geomagnetic and auroral activity obtained in recent years has contributed to a greater understanding of solar-terrestrial processes. However, because space exploration began only in the middle of the 20th century, in situ data are insufficient to analyze geomagnetic variations and solar-activity variations on a time scale from decades to centuries. The Russian network of magnetic and meteorological observatories provides one of the longest data series. For example, the magnetograms from St. Petersburg (SPE), Pavlovsk (SLU), and Voeikovo (LNN) stations provide long series of continuous records of variations of declination (D) and horizontal (H) and vertical (Z) components of the geomagnetic field. The aim of this paper is to make this data publicly available. For this purpose, a specialized database has been developed for the study of various aspects of solar-terrestrial relationships, including heliobiomagnetology. The database contains (1) digital images of analog magnetograms from SPE (1869-1877) and SLU (1878-1921, images for 1921-1941 are still being scanned), (2) hourly values of declination D and horizontal H and vertical Z components of the geomagnetic field obtained at SPE and SLU stations for 1869-1914, (3) data on geomagnetic storms from the SLU station for 1878-1941 and from the LNN station for 1947-1954, and (4) data on aurora borealis observed at 141 stations of the Russian Meteorological Network for 1837-1909. The database is designed to provide online access to the Russian collection of historical data on geomagnetic and auroral activity. On this basis, it is possible to carry out research on various aspects of space weather and climate and use it, among other things, to solve problems of heliomagnetobiology. Users are provided with easy access to individual magnetograms at different zoom levels. Online access will allow a wide range of researchers to use these databases to solve problems related to historical space weather data. [ABSTRACT FROM AUTHOR]

The annual number of magnetic storms N recorded at St. Petersburg observatories (Pavlovsk/Slutsk and Voyeykovo) in 1878-1954 is studied. The analysis shows that N has increased since ~1900 for different storm types (storms with sudden commencement Ssc and storms with gradual Sg commencement; moderate, strong and very strong); however, the number of Ssc storms increased more rapidly than the number of Sg storms. The percentage of Ssc storms doubled for the first half of the 20th century, while the number of Sg storms decreased by 1.5 times. The Ssc storms are driven by coronal mass ejections from closed magnetic structures on the Sun, and Sg storms are driven by corotating fluxes from open magnetic structures and coronal holes. These results are apparently evidence of an increase in the activity of both types of solar magnetic structures in the first half of the 20th century and a more rapid increase in the activity of fields with closed lines of forces. A semiannual variation with maxima in the periods of vernal and autumnal equinoxes is clearly pronounced for Sg and moderate storms. The tendency to have two equinoctial maxima is pronounced in the total number of storms N for both even and odd cycles; however, maxima that differ from the arithmetic mean by more than a standard deviation are observed only in September in even cycles and in March in odd cycles. [ABSTRACT FROM AUTHOR]

The 22-year variation in the frequency of aurora occurrence is found through an analysis of data of the Russian network of meteorological stations from 1837-1909. This variation is obtained in a form of asymmetry between even and odd solar cycles. We found that the nature of the 22-year variation depends on the latitude of the observation station. The annual number N of midlatitude auroras (geomagnetic latitudes Φ < 56°) for about three years at the end of the descending part of solar cycles is larger for the even cycles than for the odd. For high-latitude auroras (Φ ≥ 56°), the pattern is opposite: at the descending part of the solar cycle, N is larger in the odd cycles than in the even. For the high-latitude sector, asymmetry of the polar sun cycles (the period between two magnetic field reversals) is clearly observed: an increased N is observed during the whole odd polar cycle (which starts approximately at the maximum of the odd Schwabe cycle) as compared to the even cycle. Extrapolation of the modern picture of alternation of the sign of the global solar magnetic field back in time leads to the conclusion that the most geoeffective polar cycles in cycles 8-14 were those in which the polar magnetic field in the northen hemisphere was negative. [ABSTRACT FROM AUTHOR]

Observations of auroras in Russia from 1837 to 1900 have been catalogued on the basis of data of the Russian network of meteorological observatories. These observation data from 129 stations in the European and Asian parts of Russia cover a wide geographical zone (ϕ = 39°57′-72°30′ N and λ = 21°1′-224°35′ E). A difference was revealed between the behavior of midlatitude (Φ < 56°) and high-latitude auroras during a solar cycle. A peak in the occurrence frequency of aurora dominates at the cycle maximum in midlatitudes; there is an additional maximum during the declining phase. In contrast, the dominant occurrence frequency peak is observed during the declining phase of a solar cycle or at its minimum for high-latitude auroras. In addition, the occurrence frequency of high-latitude aurora increases in 1837-1900. An upward trend in the occurrence frequency of aurora is also observed at the St. Petersburg observatory (Pavlovsk, Φ = 56°). This trend apparently is evidence of an increase in the open regions of solar magnetic fields in 1837-1900. Some parameters of auroral activity also show a 22-year variation. [ABSTRACT FROM AUTHOR]

The model calculation of a magnetic disturbance, which was registered at Colaba observatory (India) during the historic giant magnetic storm on September 1-2, 1859, is illustrated. The calculation demonstrates that the observed, unusually fast, 2-h main phase of this storm, when the negative amplitude of the geomagnetic field vector H component was −1600 nT, and an extremely fast (1.5-h) initial field recovery phase from the maximum to the −110 nT amplitude can be generated. The following models of the magnetospheric current systems were used in the calculations: the ring current ( DR), the magnetospheric magnetopause current ( DCF), the magnetotail current system ( DT), and the high-latitude current system ( DP). The unusual time variation in the registered geomagnetic disturbance is related to the probable fast and considerable equatorward shift of the high-latitude currents during the main phase of the analyzed giant storm and to the same fast backward motion of these currents during the initial field recovery phase. The unusually large amplitude of the registered geomagnetic disturbance could have been caused by the total contribution of the indicated magnetospheric current systems during the time when the storm was generated as a result of the interaction between the magnetosphere and the solar plasma ejected during the gigantic solar flare before the storm. [ABSTRACT FROM AUTHOR]

Geomagnetic field parameters have been measured in different sites of the northwest of Russia for hundreds of years. This work presents the results of numerous measurements in St. Petersburg, as well as in the Gulf of Finland within the zone from 25° to 30°30′ E and from 59° to 61° N. The first measurements were made in the period1630-1650. For this work, archival data, provided by the Archives of the St. Petersburg Magnetic Observatory (SPbF IZMIRAN), and data from different historical records have been used. Data on the Earth's magnetic field variations in St. Petersburg have been recorded since 1726; they were analyzed and corrected to get a uniform and complete data set. The reconstructed long-term data set of magnetic variation measurements in St. Petersburg was compared with the GUFM1 historical model. This model allows us to calculate the values of all parameters of the main magnetic field in any place on the Earth since 1590. The comparative analysis carried out by us has revealed a discrepancy between the model and measured values. This discrepancy can be caused by local secular variations in the magnetic field in the St. Petersburg region. The correction of the area-averaged secular variation makes this discrepancy insignificant. [ABSTRACT FROM AUTHOR]

Great magnetic storms (geomagnetic index C9 is ≥8 for St. Petersburg, which can correspond to Kp ≥ 8 or Dst < −200 nT), registered from 1841 to 1870 at the St. Petersburg, Yekaterinburg, Barnaul, Nerchinsk, Sitka, and Beijing (at the Russian embassy) observatories are analyzed. A catalog of intensive magnetic storms during this period, which includes solar cycles 9-11, has been compiled. The statistical characteristics of great magnetic storms during this historical period have been obtained. These results indicate that high solar activity played a decisive role in the generation of very intense magnetic storms during the considered period. These storms are characterized by only one peak in a solar cycle, which was registered in the years of the cycle minimum (or slightly earlier): the number of great geomagnetic storms near the solar activity maximum was twice as large as the number of such storms during less active periods. A maximum in September-October and an additional maximum in February are observed in the annual distribution of storms. In addition, the storm intensity inversely depends on the storm duration. [ABSTRACT FROM AUTHOR]

Methods for increasing the activity of polymer catalysts of urethane formation via their heterogenization in solutions have been developed. The kinetic features have been studied for model reactions carried out in the presence of catalysts containing Bu3SnO(O)C groups at the ends of poly(ethylene glycol) chains in the solvent-precipitant system, initially heterogeneous organotin catalysts based on the styrene-maleic anhydride copolymer crosslinked by divinylbenzene, and a modified silica gel prepared by the surface grafting of tributyltin acetate groups. Unlike the use of monomeric organotin catalysts of urethane formation, whose catalytic activity attains a plateau with an increase in their concentration in solutions, the use of heterogeneous catalysts results in linear dependences of the reaction rate on the concentration of catalytic centers. [ABSTRACT FROM AUTHOR]

The kinetics of the thermal decomposition and rearrangement of benzoyl azide into phenyl isocyanate was studied in n-heptane in the presence of boron trifluoride etherate as the catalyst. The apparent activation energy of the noncatalytic reaction is 28.0 kcal/mol, and that of the catalytic reaction is 11.0 kcal/mol. The electronic structure and geometry of various complexes between benzoyl azide and BF3 were studied using the PBE/TZ2P density functional method, and fragments of the potential energy surface were calculated for the catalytic rearrangement. Comparatively stable 1: 1 and 1: 2 complexes between the syn conformer of benzoyl azide and the catalyst can form in the system by coordination to the oxygen and nitrogen atoms of the acyl azide group. The heats of formation of these complexes are between −1.7 and −6.4 kcal/mol. The main consequence of the formation of these complexes is that the acyl azide group comes out of the benzene ring plane and thus becomes more reactive. The effective activation energies calculated for the catalytic rearrangement involving complexes of different compositions are 12–15 kcal/mol lower the effective activation energy of the noncatalytic reaction. Information has been obtained about the structure of the transition state of the catalytic reaction, in which a nitrogen molecule is abstracted from benzoyl azide with a synchronous rearrangement of other atoms, resulting in the formation of the ultimate product. [ABSTRACT FROM AUTHOR]

A retrospective analysis of the Russian magnetic observations of the Carrington event that occurred on September 2–3, 1859, has been performed. The conclusion has been made that this event was caused by the series of three recurrent eruptive solar flares during ∼40 h. The characteristics of the geomagnetic crochet, related to a considerable flux of the ionizing electromagnetic radiation during this flare, have been studied. The value and direction of a magnetic field disturbance, registered during the maximum of the geomagnetic storm of September 2, unambiguously indicate that all Russian stations were in the auroral oval zone, which was strongly expanded southward from its average position. The disturbance dependence on the station longitude—the absence of magnetometer pinning in Nerchinsk—is interpreted as the possible manifestation of a strong asymmetry in the effective contour of the current system, which was connected to the heliosphere and covered the disturbed magnetosphere and ionosphere during the short period that lasted only 1–3 h. [ABSTRACT FROM AUTHOR]

Based on an analysis of the available archived data from the Russian network of geomagnetic stations, it has been indicated that the known event of August–September 1859 was the first and the greatest event in the series of the recurrent geomagnetic storms. Similar series were repeatedly observed in the next years. These series are caused by the processes on the Sun and in the heliosphere related to the superposition of the solar wind flows. The sporadic and regular components in joint activity of the complex, including active regions and coronal holes on the rotating Sun, play the role of the Bartels M regions responsible for initiation and development of geomagnetic storms. Neither coronal holes nor active regions can separately explain observations. During interpretation, active regions and coronal holes should be considered as a unified complex. [ABSTRACT FROM AUTHOR]

Geomagnetic variations generate electric currents in long conductors such as high-voltage lines, pipelines, and telecoms cables. The aim of our work is to study the possible effect of geomagnetic disturbances on the operation of automated systems and telemechanics of a midlatitude railroad based on the data on the malfunctions and breakdowns registered in 2004 on the East Siberian railroad (VSZhD). It has been obtained that the total daily duration of malfunctions and breakdowns ( T) during disturbed periods is controlled by geomagnetic activity. When a peak of geomagnetic activity is reached during a storm, T increases about three times. Moreover, a correlation between T and the local index of geomagnetic activity ( A), measured at Podkamennaya Tunguska Siberian observatory, is high during disturbed periods. Specifically, the correlation coefficient ( K) is equal to 0.83 and 0.71 for the strongest two storms of 2004 that occurred in July 17–August 2 and November 4–18, respectively. [ABSTRACT FROM AUTHOR]

Comet outburst activity and the structure of solar wind streams were compared on the basis of Pioneer 10, 11, Vela 3 and IMP 7, 8 measurements at the heliocentric distance r ≈ 1-6 AU. It is shown that the solar wind velocity waves which are evolving into corotating shock waves beyond the Earth orbit may be responsible for comet outburst activity. The correlation between variations of comet outburst activity with heliocentric distance and the behavior of the solar wind velocity waves is established. The closeness of the characteristic times for the velocity waves and comet outburst activity (7-8 days at r = 1 AU) as well as the simultaneous growth of both the characteristic times with r are noted. The observed distribution of the comet outburst activity parameters during the 11-year cycle is also in good agreement with the phase distributions during the 11-year cycle of variations of the coronal hole areas and the rate of change of the sunspot area δ S . [ABSTRACT FROM AUTHOR]