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Ar production rates from the Homestake experiment suggest a possible anticorrelation between solar neutrino flux and solar activity. In this paper we present results from linear correlation analyses between Homestake data and several solar activity parameters in the period 1970–1990. Our results support the hypothesis that Homestake neutrino fluxes exhibit a (positive or negative) correlation with those parameters, but they also suggest that the heliomagnetic field in the subphotosphere could be responsible for the observed flux modulation. 相似文献
2.
To investigate the long-term modulation of galactic cosmic rays at the ground-based detector energies, the monthly values of the neutron monitor (Climax, Mt. Washington, Deep River, and Huancayo) and ionization chamber (Cheltenham/Fredericksburg, Huancayo, and Yakutsk) intensities have been correlated with the sunspot numbers (used as a proxy index for transient solar activity) for each phase of sunspot cycles 18 to 22. Systematic differences are found for results concerning odd and even sunspot cycles. During odd cycles (19 and 21) the onset time of cosmic-ray modulation is delayed when compared with the onset time of the sunspot cycle, while they are more similar during even (18, 20, and 22) cycles. Checking the green corona data, on a half-year basis, we found typical heliolatitudinal differences during ascending phases of consecutive sunspot cycles. This finding suggests a significant role of the latitudinal coronal behaviour in the heliospherical dynamics during a Hale cycle. Such effectiveness concerns not only the transient interplanetary perturbations but also the recurrent ones. In fact, when lag between cosmic-ray data and sunspot numbers is considered, the anticorrelation between both parameters is very high (correlation coefficient |r| > 0.9) for all the phases considered, except for the declining ones of cycles 20 and 21, when high-speed solar wind streams coming from coronal holes affect the cosmic-ray propagation, and theRz parameter is no longer the right proxy index for solar-induced effects in the interplanetary medium. 相似文献
3.
The relationship between the galactic cosmic ray modulation (CR) and the non-flare coronal level, as given by the solar soft X-ray background (XBG), is investigated from 1 July 1968 to 30 June 1980 on a daily basis. The stationarity problem of a multivariate time series, as well as the role of the short- and medium-term corona variability are faced. From them it is found that the CR/XBG relation is variable during the considered heliomagnetic semicycle, while CR and XBG are highly anticorrelated on a long-time scale (12-month averages). The CR/XBG relationship during the declining phase of solar activity shows a moderately strong anticorrelation, on short- and medium-term time scales (coefficient up to –0.77 for 27-day running averages), went towards insignificant values in the minimum phase and is only partially reconstructed during the rise of the following solar cycle. During the solar activity maximum of cycle 20 the cosmic-ray modulation is only related to the short-term coronal fluctuations (no other time scales are significant, supporting the reliability of the so-called `Gnevyshev gap' in solar parameters). 相似文献
4.
V. Mussino O. Borello Filisetti M. Storini H. Nevanlinna 《Annales Geophysicae》1994,12(10-11):1065-1070
Monthly averages of the Helsinki Ak-values have been reduced to the equivalent aa-indices to extend the aa-data set back to 1844. A periodicity of about five cycles was found for the correlation coefficient (r) between geomagnetic indices and sunspot numbers for the ascending phases of sunspot cycles 9 to 22, confirming previous findings based on a minor number of sunspot cycles. The result is useful to researchers in topics related to solar-terrestrial physics, particularly for the interpretation of long-term trends in geomagnetic activity during the past, and to forecast geomagnetic activity levels in the future. 相似文献
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The long-time series of daily means of cosmic-ray intensity observed by four neutron monitors at different cutoff rigidities (Calgary, Climax, Lomnický tít and Huancayo/Haleakala) were analyzed by means of the wavelet transform method in the period range 60 to 1000 days. The contributions of the time evolution of three quasi-periodic cosmic-ray signals (150 d, 1.3 yr and 1.7 yr) to the global one are obtained. While the 1.7-yr quasi-periodicity, the most remarkable one in the studied interval, strongly contributes to the cosmic ray intensity profile of solar cycle 21 (particularly in 1982), the 1.3-yr one, which is better correlated with the same periodicity of the interplanetary magnetic field strength, is present as a characteristic feature for the decreasing phases of the cycles 20 and 22. Transitions between these quasi-periodicities are seen in the wavelet power spectra plots. Obtained results support the claimed difference in the solar activity evolution during odd and even solar activity cycles. 相似文献
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A good knowledge of coronal hole (CH) evolution in time is relevant for the understanding of the decay and/or the stability of large-scale magnetic fields in the different heliographic latitudinal belts. Using a CH catalogue, mainly compiled from the Hei line (10830 Å) measurements (Sanchez-Ibarra and Barraza-Paredes, 1992, and updated from the NOAA/Boulder Web pages), some characteristics of the CH behaviour in the solar activity cycles 21 and 22 are identified and described. We found: (i) the total number distributions for the isolated and polar coronal holes are similar, (ii) there is a north/south asymmetry, with a northern dominance in the number distribution of the polar coronal holes, (iii) a hint of a 22-year periodicity in the CH behaviour. In addition, two pairs of two isolated CHs with opposite polarity, maximum ages of more than 14 Carrington rotations, separated by about two years, are found during the early decreasing activity phase of each cycle. 相似文献
7.
Bazilevskaya G.A. Krainev M.B. Makhmutov V.S. Flückiger E.O. Sladkova A.I. Storini M. 《Solar physics》2000,197(1):157-174
A distinctive peak and gap structure in a number of solar indices was observed in the maximum phase of solar cycles 21 and 22. The effect became even more prominent after separating the northern and southern solar hemispheres. In cycle 21 the multi-peaked structures observed in the two solar hemispheres were not synchronous and their sum resulted in the rather shallow two-peaked solar maximum for the parameters taken over the whole solar disk. In cycle 22 there were only double peaks in each hemisphere which were rather synchronous. Examination of solar activity in the northern and southern hemispheres has shown that the structured maximum appears to be due to the superposition of two quasi-oscillating processes with characteristic time-scales of 11 years and of 1–3 years (quasi-biennial oscillations). The absolute amplitude of the quasi-biennial oscillations depends on the 11-year cycle phase and reaches its maximum at the maximum of the 11-year cycle. This explains the occurrence of a double- or triple-peak structure in the solar maximum phase. 相似文献
8.
Ilya G. Usoskin Laurent Desorgher Peter Velinov Marisa Storini Erwin O. Flückiger Rolf Bütikofer Gennady A. Kovaltsov 《Acta Geophysica》2009,57(1):88-101
A brief review of the research of atmospheric effects of cosmic rays is presented. Numerical models are discussed, that are
capable to compute the cosmic ray induced ionization at a given location and time. Intercomparison of the models, as well
as comparison with fragmentary direct measurements of the atmospheric ionization, validates their applicability for the entire
atmosphere and the whole range of the solar activity level variations. The effect of sporadic solar energetic particle events
is shown to be limited on the global scale, even for the most severe event, but can be very strong locally in polar regions,
affecting the physical-chemical properties of the upper atmosphere, especially at high altitudes. Thus, a new methodology
is presented to study cosmic ray induced ionization of the atmosphere in full detail using realistic numerical models calibrated
to direct observations. 相似文献
9.
Comparison of Earth’s magnetospheric magnetic field models in the context of cosmic ray physics 总被引：1，自引：0，他引：1
Laurent Desorgher Karel Kudela Erwin O. Flückiger Rolf Bütikofer Marisa Storini Vladimir Kalegaev 《Acta Geophysica》2009,57(1):75-87
Over the last two decades, models of the Earth’s magnetospheric magnetic field have been continuously improved to describe
more precisely the different magnetospheric current systems (magnetopause current, symmetric and partial ring currents, tail
currents and field aligned currents). In this paper we compare the different Tsyganenko models and the Alexeev and Feldstein
model in the context of cosmic ray physics. We compare the vertical cutoff rigidity and asymptotic direction of vertical incidence
obtained with these models for the January 20, 2005, ground level enhancement and for the big magnetic storm of April 6, 2000.
For the event of January 20, 2005, we study the impact of the differences in asymptotic direction obtained with the models
on the radiation dose computation at aircraft altitude. For the magnetic storm of April 6, 2000, we discuss the importance
of the different magnetospheric current systems in causing cutoff rigidity variations. Finally we summarise the advantages
and drawbacks of the different models in the context of space weather. 相似文献
10.
The existence of a 22-year heliomagnetic cycle was inferred long ago not only from direct measurements of the solar magnetic field but also from a cyclic variability of a number of the solar activity phenomena. In particular, it was stated (a rule derived after Gnevyshev and Ohl (1948) findings and referenced as the G–O rule in the following) that if sunspot number Rz cycles are organized in pairs of even–odd numbered cycles, then the height of the peak in the curve of the yearly-averaged sunspot numbers Rz-y is always lower for a given even cycle in comparison with the corresponding height of the following odd cycle. Exceptions to this rule are only cycles 4 and 8 which, at the same time, are the nearest even cycles to the limits of the so-called Dalton minimum of solar activity (i.e., the 1795–1823 time interval). In the present paper, we are looking for traces of the mentioned G–O rule in green corona brightness (measured in terms of the Fexiv 530.3 nm emission line intensity), using data covering almost five solar cycles (1943–1994). It was found that the G–O rule seems to work within the green-line corona brightness, namely, when coronal intensity measured in an extended solar middle-latitude zone is considered separately from the rest of the solar surface. On the other hand, the same G–O rule is valid at the photospheric level, as the heliographic latitudinal dependence of sunspot numbers (1947–1984) shows. 相似文献
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