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1.
Based on observations of long-term variations in galactic cosmic rays (CRs) on Earth and in the near-Earth space, we have determined, using our own semiempirical model, modulation of galactic CRs during solar cycles 19–23. The modulation model relates CR variations to the characteristics of the solar magnetic field obtained for the surface of the solar wind source at distances of 2.50 and 3.25 solar radii. The main focus is CR behavior at the minimums of cycles 19–23 and specific features of CR modulation at a prolonged (as compared to previous cycles) minimum of cycle 23, which is still ongoing. CR modulation at minimums related to a change in the solar field dipole component during this period of the cycle has been considered. It is indicated that the long-term variations in CRs are better described if the last two years (2007 and 2008) of cycle 23 with anomalously low solar activity (SA) are included in the model. The role and value of the contribution of the cyclic variations in each index used in the proposed CR modulation model to the observed CR modulation have been estimated.  相似文献   

2.
It is proposed to determined minimums of the 11-year solar cycles based on a minimal flux of the large-scale open solar magnetic field. The minimal fluxes before the finished cycle 23 (Carrington rotation CR 1904) and the started cycle 24 (CR 2054, April 2007) were equal to 1.8 × 1022 and 1.2 × 1022 μs, respectively. The long-term tendency toward an approach to a deep minimum of solar activity is confirmed. On the assumption that magnetic flux variations from minimums to maximums are proportional to each other, the anticipated value of the maximal Wolf number during cycle 24 is estimated as W max = 80.  相似文献   

3.
The magnetospheric storm on November 20, 2003 was one of two greatest events in 1957–2003. The D st* index reached −472 nT, the polar cap potential drop exceeded 200 kV, the polar cap boundary expanded up to Φ = 60°, the plasma layer density in the synchronous orbit reached 5 cm−3, and the inner edge of the plasma sheet penetrated up to L ∼ 1.5R E. The sequence of disturbance modes including some previously unknown is described. The distribution of the total power input into the magnetosphere between the ionosphere (power Q i) and the ring current (Q DR), as well as the relative roles of the spontaneous substorms and the driven disturbances in the creation of the DR current, is analyzed. The values of the parameter α = Q DR/Q i are calculated with a step of 5 min. It is shown that intervals with α ≪ 1 and with maximums α ≫ 1 were observed in the events under consideration. These results contradict the dominant opinion that the energy input into the magnetosphere during disturbances is primarily dissipated in the ionosphere. The two types of α maximums are observed: one in the mode of a prevailing spontaneous substorm and the other in the mixed mode of the substorm and driven disturbance. It is concluded that both types of the maximums and corresponding enhancements of the DR current appeared due to the plasma turbulization processes in the substorm current wedge. The parameter α appears to slowly increase from α ≪ 1 to α > 1 with increasing activity level; this trend supports the driven model of creating the DR current due to an increase in the electric field of the solar wind.  相似文献   

4.
The features of the amplitude distributions of magnetic impulse events have been investigated using the observations from a number of high-latitude observatories in the Northern and Southern hemispheres. It has been shown that the tails of the statistical distribution functions of the impulse amplitudes are approximated by a power law of the form f(A) = A −α, where A is the impulse amplitude and α is the exponent. Therefore, the magnetic-impulse generation regime corresponds to the features of the on-off intermittency model. The distribution of the magnetic impulse amplitudes has been analyzed for various geomagnetic latitudes, local times, seasons, solar activity cycle phases, and interplanetary conditions. It has been found that most statistical distributions of magnetic impulse amplitudes have the exponent α larger than 2, which is typical of the chaotic regimes called “strong turbulence.” In some cases, the exponent α is close to 1, which is typical of the regimes generated in a weakly turbulent medium. Qualitative estimates of the plasma wave turbulence level in the high-latitude magnetosphere have been obtained.  相似文献   

5.
The causes of the formation of neutral gas temperature and density equatorial minimums on the dayside, recently detected from satellite measurements, have been studied based on a global numerical model of the Earth’s upper atmosphere (UAM). The performed numerical experiments made it possible to conclude that these minimums are not related to the magnetospheric sources of energy and momentum and electric fields of the dynamo origin. It has been indicated that the absorbed solar ionizing radiation and rotation of the Earth are responsible for the formation of the neutral gas temperature and density equatorial minimums on the dayside.  相似文献   

6.
In this paper, we review the variation of the 11-year solar cycle since the 15th century revealed by the measurement of radiocarbon content in single-year tree-rings of Japanese cedar trees. Measurements of radiocarbon content in absolutely dated tree-rings provide a calibration curve for accurate dating of archaeological matters, but at the same time, enable us to examine the variations of solar magnetic activity in the pre-historical period. The Sun holds several long-term quasi-cyclic variations in addition to the fundamental 11-year sunspot activity cycle and the 22-year polarity reversal cycle, and it is speculated that the property of the 11-year and the 22-year solar cycle varies in association with such long-term quasi-cycles. It is essential to reveal the details of solar variations around the transition time of solar dynamo for illuminating the mechanisms of the long-term solar variations. We therefore have investigated the property of the 11-year and 22-year cycles around the two grand solar minima; the Maunder Minimum (1645–1715 AD) and the Spoerer Minimum (1415–1534 AD), the periods of prolonged sunspot minima. As a result, slight stretching of the “11-year” and the “22-year” solar cycles was found during these two grand solar activity minima; continuously during the Maunder Minimum and only intermittently during the Spoerer Minimum. On the contrary, normal or slightly shortened 11-year cycles were detected during the interval period of these two minima. It suggests the inverse correlation between the solar cycle length and solar magnetic activity level, and also the change of meridional flow during the grand solar activity minima. Further measurements for the beginning of the grand solar minima will provide a clue to the occurrence of such prolonged sunspot disappearance. We also discuss the effect of solar variations to radiocarbon dating.  相似文献   

7.
A simple finite-dimensional geodynamo model, obtained from the equations of the mean field electrodynamics and reproducing the phenomenon of geomagnetic reversals, is proposed. It has been indicated that the reversal scale obtained in the scope of this model is rather close to the observed scale in its properties. The reversal mechanism is related to the α-effect fluctuations. It is not necessary to substantially change the hydrodynamic parameters of the problem so that a reversal originates in the scope of such a model, but it is only sufficient to take the α-effect fluctuations into account. If the rms deviation of fluctuations accounts for 10% of the average α value, a fluctuation of two-three standard deviations is sufficient for the origination of a reversal, which quite agrees with the concept that reversals are rather rare phenomena. Another factor resulting in the regime with reversals is that the model can generate magnetic fields with different behaviors in different regions of the parametric space in linear mode: monotonically increasing fields and fields increasing with oscillations.  相似文献   

8.
The parameter of cosmic ray fluctuations, which indicates the degree of IMF inhomogeneity, was introduced in order to quantitatively describe the dynamics of the galactic cosmic ray (GCR) intensity fluctuations during the geoeffective phases of the 11-year cycle. The 5-min data of the high-latitude neutron monitor at Oulu station (Finland) during cycles 20–23 was used in the calculations. The nonrandom non-Gaussian character of the GCR fluctuation parameter is caused by the nonstationary semiannual variation reflecting the transient nonstationary oscillatory process of sign reversal of the general solar magnetic field. This transient oscillatory process is responsible for the maximal geoeffectiveness and duration of the phase of polarity reversal, which manifests itself in a sharp and deep GCR intensity minimum during the final stage of the field sign reversal. The invariant of the 11-year “amplitude-duration” cycle was confirmed on a new basis: the LF drift of the “low” cycle period was detected, which was observed in an increase in the duration of cycle 23 we anticipated.  相似文献   

9.
The linkage between multi-decadal climate variability and activity of the sun has been long debated based upon observational evidence from a large number of instrumental and proxy records. It is difficult to evaluate the exact role of each of solar parameters on climate change since instrumentally measured solar related parameters such as Total Solar irradiance (TSI), Ultra Violet (UV), solar wind and Galactic Cosmic Rays (GCRs) fluxes are more or less synchronized and only extend back for several decades. Here we report tree-ring carbon-14 based record of 11-year/22-year solar cycles during the Maunder Minimum (17th century) and the early Medieval Maximum Period (9–10th century) to reconstruct the state of the sun and the flux of incoming GCRs. The result strongly indicates that the influence of solar cycles on climate is persistent beyond the period after instrumental observations were initiated. We find that the actual lengths of solar cycles vary depending on the status of long-term solar activity, and that periodicity of the surface air temperatures are also changing synchronously. Temperature variations over the 22-year cycles seem, in general, to be more significant than those associated with the 11-year cycles and in particular around the grand solar minima such as the Maunder Minimum (1645–1715 AD). The polarity dependence of cooling events found in this study suggests that the GCRs can not be excluded from the possible drivers of decadal to multi-decadal climate change.  相似文献   

10.
The event of March 12–19, 2009, when a moderately high-speed solar wind stream flew around the Earth’s magnetosphere and carried millihertz ultralow-frequency (ULF) waves, has been analyzed. The stream caused a weak magnetic storm (D st min = −28 nT). Since March 13, fluxes of energetic (up to relativistic) electrons started increasing in the magnetosphere. Comparison of the spectra of ULF oscillations observed in the solar wind and magnetosphere and on the Earth’s surface indicated that a stable common spectral peak was present at frequencies of 3–4 mHz. This fact is interpreted as evidence that waves penetrated directly from the solar wind into the magnetosphere. Possible scenarios describing the participation of oscillations in the acceleration of medium-energy (E > 0.6 MeV) and high-energy (E > 2.0 MeV) electrons in the radiation belt are discussed. Based on comparing the event with the moderate magnetic storm of January 21–22, 2005, we concluded that favorable conditions for analyzing the interaction between the solar wind and the magnetosphere are formed during a deep minimum of solar activity.  相似文献   

11.
The possibilities of improving the semiempirical model of cosmic ray (CR) modulation, proposed by us previously, are discussed. The following characteristics have been considered as model parameters in order to describe long-period CR variations using a unified model and to more completely reflect solar cycles in CR modulation as a complex interaction between two systems of fields (large-scale and local): the value and sign of the polar solar field, the average strength of the solar magnetic field (the B ss integral index), partial indices (zone-even (ZE) and zone-odd (ZO) and sector-even (SE) and sector-odd (SO) indices), the tilt of the heliospheric current sheet, and the special index (F x ) taking into account X ray flares. The role of each index in CR modulation has been revealed. When we described the long-term CR variations using many parameters and taking into account the integral index or one of four partial indices, the best results of modulation modeling during 1976–1999 were obtained for the B ss total energetic index and SO index. A difference between the model calculations and observations increases beginning from the middle of 2000; the problem features of the CR behavior and the specific features of modeling this behavior in cycle 23 of solar activity (SA) are discussed. It is assumed that a decrease in the CR density at the last SA minimums (from cycle to cycle) can be related to a decrease in the ZO index and to a recently detected similar decrease in the vertical component of the solar dipole magnetic moment.  相似文献   

12.
Time variations in strong and weak photospheric magnetic fields have been considered based on synoptic maps from the Kitt Peak observatory for 1976?C2003. The magnetic fields of positive and negative polarities of the Northern and Southern hemispheres of the Sun and their imbalance were studied. It has been indicated that different groups of magnetic fields vary with 11-or 22-year periods depending on their values. The difference between positive and negative fluxes for each hemisphere always varies with a 22-year period. For weak fields, the 22-year cycle is related to the manifestation of the global solar magnetic field. For strong fields, the imbalance between positive and negative fluxes reflects the predominant role of leading sunspots in a given solar hemisphere. It has been detected that the total magnetic flux over the entire solar disk varies with an 11-year period in antiphase with the solar activity cycle for the weakest magnetic fields (0?C5 G).  相似文献   

13.
The work describes the results of calculations obtained with the Atmospheric Research Model (ARM) general circulation model. The temperature response of the troposphere and middle atmosphere to variations in UV solar radiation were found to have a large-scale wave structure when planetary waves at the lower model boundary were taken into account. In the present paper, the results from the processing of global temperature fields with three databases (ERA-20C, NOAA-CIRES 20th Century Reanalysis, v2, and NCEP/NCAR Reanalysis I) are provided. Analysis of the differences of the mean monthly temperature global fields (January and July) between the maxima and minima of three solar activity cycles (21, 22, and 23 cycles) also demonstrated their nonzonal structure. It was shown that the amplitude of this difference in January in the stratosphere (10 hPa) can be 7–29 K in the Northern Hemisphere. In July, this effect is prominent in Southern Hemisphere. In the troposphere (500 hPa), a nonzonal temperature effect is present in both the Northern and Southern Hemispheres; the amplitude of the effects amounts to approximately 5–12 K. In conclusion, we discuss that the mechanism of solar energy impact on atmospheric temperature discovered by numerical modeling is supported after reanalysis data processing.  相似文献   

14.
Measurements of solar cosmic ray (SCR) protons in the magnetosphere can be used to verify models of the Earth’s magnetic field. The latitudinal profiles of precipitating SCRs with energies of 1–90 MeV were measured on the CORONAS-F low-orbiting satellite during a strong magnetic storm on October 29–30, 2003. A flux of precipitating protons can remain equal to the interplanetary flux only due to a strong pitch angle diffusion that originates when the radius of the field line curvature is close to that of the particle rotation Larmor radius. The observed boundaries of the strong diffusion region can be compared with the boundaries anticipated according to the models of the magnetic field of the Earth’s magnetosphere. The adiabaticity parameter values, calculated for several instants of the CORONAS-F satellite pass based on the TS05 and parabolic models, do not always correspond to measurements. How possible changes in the model configurations of the magnetic field can allow us to eliminate discrepancies with the experiment and to explain why solar protons with energies of several megaelectronvolts penetrate deep in the Earth’s inner magnetosphere is considered here.  相似文献   

15.
Small-scale (scales of ∼0.5–256 km) electric fields in the polar cap ionosphere are studied on the basis of measurements of the Dynamics Explorer 2 (DE-2) low-altitude satellite with a polar orbit. Nineteen DE-2 passes through the high-latitude ionosphere from the morning side to the evening side are considered when the IMF z component was southward. A rather extensive polar cap, which could be identified using the ɛ-t spectrograms of precipitating particles with auroral energies, was formed during the analyzed events. It is shown that the logarithmic diagrams (LDs), constructed using the discrete wavelet transform of electric fields in the polar cap, are power law (μ ∼ s α). Here, μ is the variance of the detail coefficients of the signal discrete wavelet transform, s is the wavelet scale, and index α characterizes the LD slope. The probability density functions P(δE, s) of the electric field fluctuations δE observed on different scales s are non-Gaussian and have intensified wings. When the probability density functions are renormalized, that is constructed of δE/s γ, where γ is the scaling exponent, they lie near a single curve, which indicates that the studied fields are statistically self-similar. In spite of the fact that the amplitude of electric fluctuations in the polar cap is much smaller than in the auroral zone, the quantitative characteristics of field scaling in the two regions are similar. Two possible causes of the observed turbulent structure of the electric field in the polar cap are considered: (1) the structure is transferred from the solar wind, which is known to have turbulent properties, and (2) the structure is generated by convection velocity shears in the region of open magnetic field lines. The detected dependence of the characteristic distribution of turbulent electric fields over the polar cap region on IMF B y and the correlation of the rms amplitudes of δE fluctuations with IMF B z and the solar wind transfer function (B y 2 + B z 2)1/2sin(θ/2), where θ is the angle between the geomagnetic field and IMF reconnecting on the dayside magnetopause when IMF B z < 0, together with the absence of dependence on the IMF variability are arguments for the second mechanism.  相似文献   

16.
The topology and dynamics of the three-dimensional magnetic field in the solar atmosphere govern various solar eruptive phenomena and activities, such as flares, coronal mass ejections, and filaments/prominences. We have to observe and model the vector magnetic field to understand the structures and physical mechanisms of these solar activities. Vector magnetic fields on the photosphere are routinely observed via the polarized light, and inferred with the inversion of Stokes profiles. To analyze these vector magnetic fields, we need first to remove the 180° ambiguity of the transverse components and correct the projection effect. Then, the vector magnetic field can be served as the boundary conditions for a force-free field modeling after a proper preprocessing. The photospheric velocity field can also be derived from a time sequence of vector magnetic fields.Three-dimensional magnetic field could be derived and studied with theoretical force-free field models, numerical nonlinear force-free field models, magnetohydrostatic models, and magnetohydrodynamic models. Magnetic energy can be computed with three-dimensional magnetic field models or a time series of vector magnetic field. The magnetic topology is analyzed by pinpointing the positions of magnetic null points, bald patches, and quasi-separatrix layers. As a well conserved physical quantity,magnetic helicity can be computed with various methods, such as the finite volume method, discrete flux tube method, and helicity flux integration method. This quantity serves as a promising parameter characterizing the activity level of solar active regions.  相似文献   

17.
Relative variations in the number of sunspots and sunspot groups in activity cycles have been analyzed based on data from the Kislovodsk Mountain Astronomical Station and international indices. The following regularities have been established: (1) The relative fraction of small sunspots decreases linearly and that of large sunspots increase with increasing activity cycle amplitude. (2) The variation in the average number of sunspots in one group has a trend, and this number decreased from ～12 in cycle 19 to ～7.5 in cycle 24. (3) The ratio of the sunspot index (Ri) to the sunspot group number index (G gr) varies with a period of about 100 years. (4) An analysis of the sunspot group number index (G gr) from 1610 indicates that the Gnevyshev-Ohl rule reverses at the minimums of secular activity cycles. (5) Ratio of the total area to area of Ssp/Sum nuclei has long-term variation with a period approximately 8 cycles. Minimum ratio falls on 16–17 cycles of activity. (6) It has been indicated that the magnetic field intensity and sunspot area in the current cycle are related to the amplitude of the next activity cycle.  相似文献   

18.
The paper deals with the relation of long-term variations of 10 GV galactic cosmic rays (GCR) to the global solar magnetic field and solar wind parameters. This study continues previous works, where the tilt of the heliospheric current sheet (HCS) and other solar-heliospheric parameters are successfully used to describe long-term variations of cosmic rays in the past two solar cycles. The novelty of the present work is the use of the HCS tilt and other parameters reconstructed from Hα observations of filaments for the period when direct global solar magnetic field observations were unavailable. Thus, we could extend the GCR simulation interval back to 1953. The analysis of data for 1953–1999 revealed a good correlation (the correlation coefficient >0.88) between the solar-heliospheric parameters and GCR in different cycles of solar activity. Moreover, the approach applied makes it possible to describe the behavior of cosmic rays in the epochs of solar maxima, which could not be done before. This indicates both the adequacy of the model and the reliability of the reconstructed global solar magnetic field parameters.  相似文献   

19.
In this paper, we consider variations in energetic electron fluxes at a geostationary orbit, which are related to the Sun’s rotation period, during two solar cycles. We use data on energetic electron fluxes obtained from the GOES (1986–2007) (>2 MeV) and LANL (1996–2007) (50–225 and 315–1500 keV) satellites. Within the solar cycle, we observed both periods of high flux peak recurrence during several rotations and periods when there was no (or a low) 27-day recurrence. We show the similarity and difference between manifestations of flux recurrences from cycle to cycle. Insignificant manifestation of recurrence and its absence were observed mainly during the solar maximum. High electron flux recurrence was observed mainly at the phase of decline in solar activity (near the solar minimum). We show that for both solar cycles, there were several days (within the Bartels rotation) during which increased energetic electron fluxes would be most likely observed.  相似文献   

20.
The studies are based on the experimental mass sounding of the interplanetary plasma near the Sun at radial distances of R = 4−70 R S, performed at Pushchino RAO, Russian Academy of Sciences, and on the calculated magnetic fields in the solar corona based on the magnetic field strength and structure measured on the Sun’s surface at J. Wilcox Solar Observatory, United States. The experimental data make it possible to localize the position of the boundary closest to the Sun of the transition transonic region of the solar wind in the near-solar space (R ≈ 10−20 R S) and to perform an interrelated study of the solar wind structure and its sources, namely, the magnetic field components in the solar corona based on these data. An analysis of the evolution of the flow types in 2000–2007 makes it possible to formulate the physically justified criterion responsible for the time boundaries of different epochs in the solar activity cycle.  相似文献   

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