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The dependence of cosmic-ray intensity on 21st solar cycle phenomena has been studied using monthly cosmic-ray values from nine world wide Neutron Monitoring Stations.For this purpose the long-term cosmic-ray modulation is modelled by treating the most appropriate source functions among various solar, interplanetary and terrestrial activity indices as the input and the cosmic-ray intensity as the output of a linear system taking into account the corresponding time-lag. In this way the modulated galactic cosmic-ray intensity has been reproduced to a certain degree as the cosmic-ray variations follow the observations with a standard deviation of ~ 10%. Still remaining short-term variations in all stations with periods of 2.7 and 3.7 months can possibly be related to the galactic origin of cosmic-rays.The Simpson solar wind model improved by the spherically symmetric diffusion-convection theory can describe our proposed method. 相似文献
2.
Sector-structured interplanetary magnetic field associated with the fast plasma streams in 1985–1996
An analysis of 373 well-defined high-speed solar-wind streams observed at 1 AU during the years 1985–1996 is outlined. The distribution of the occurrence of these streams as a function of Bartels rotation days using the dominant polarity of the interplanetary magnetic field (IMF) associated with the referred fast streams shows that a four-sector pattern for the positive IMF polarity and a two-sector pattern for the negative IMF polarity are the dominant features in the investigated period. The high-speed streams seem to occur at preferred Bartels days: positive polarity streams are most frequent near Bartels days 5 and 18, while negative polarity streams are most frequent in days 14 and 23. Moreover, the corotating streams with positive IMF polarity prefer to occur in days 5 and 18 of the Bartels rotation period, whereas flare-generated streams with negative IMF polarity occur in days 14 and 23. The observed distribution of Bartels days is probably related to the distribution of the solar sources of high-speed solar wind streams as the solar wind carries with it the photospheric magnetic polarity of the solar source region. In addition, the distribution of the streams reveals a similar behaviour during the ascending and the declining phase of the last solar cycle (22nd) in contrast to the previous one where it has an opposite appearance. Determined differences in the characteristics of the sector structured IMF associated with the fast streams of the last cycle with the previous one (21st) and some similarities with the alternate solar cycle (20th) seem to be attributed to the 22-year magnetic cycle and to the polarity reversals of the polar magnetic field of the Sun. As the magnetic sectors are due to multiple crossings of the solar equatorial plane by a large-scale, warped heliospheric current sheet, it is suggested that the two-sector pattern arises from a tilted solar magnetic dipole component and the more commonly observed four-sector pattern from a quadrupole component of the solar interplanetary magnetic field. 相似文献
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A reference catalogue of 373 well-defined high-speed plasma streams identified in the solar wind measurements from 1985 to 1996 is reported. The data base for this study is the interplanetary plasma/magnetic field data compilation made available by the NSSDC/WDC-A for rockets and satellites (NASA/GSFC-Greenbelt). The main characteristics of those streams, such as the beginning time, the duration, the origin of them (corotating or flare-generated), the interplanetary magnetic field polarity (Stanford magnetic field), are given in the catalogue.The long-term variation in the occurrence rate of high-speed streams shows interesting differences between even and odd solar cycles when catalogues for solar cycles 20, 21, and 22 are considered together. Hence, this catalogue, extended now over three solar cycles, should be useful for studies connected with solar-interplanetary or solar-terrestrial phenomena, and to clarify solar activity in time. 相似文献
4.
Selecting the most appropriate source functions among the various solar, interplanetary and terrestrial activity indices we have attempted to reproduce to a certain degree the long-term modulation of galactic cosmic-rays. For this study monthly cosmic-ray data from nine world-wide neutron monitor stations for the period 1975–1985 have been analysed. The empirical formula which has been used to compute the long-term cosmic-ray variations follows the observations fairly well.It is noteworthy that the residuals in the cosmic-ray intensity between that observed and that calculated by this empirical formula exhibits a still remaining short-term variation in all stations of 2.7 and 3.7 months. Possible interpretations of these observed periodicities related to galactic origin are given. 相似文献
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J. Xanthakis H. Mavromichalaki B. Petropoulos E. Marmatsouri A. Vassilaki 《Earth, Moon, and Planets》1988,43(2):165-179
A three-dimensional model for the calculation of cosmic-ray intensity of the Inuvik station during the 20th and 21st solar cycles is given. Especially we have studied the coefficient K of the used parameter of sunspot number in terms of high-speed solar-wind streams and have tried enough successfully to relate this coefficient with the diffusion process of cosmic rays in the interplanetary space.Analyzing these two data sets for the time-period 1964–1985 into a network of trigonometric series we have observed similar period in the two sets. It means that we have the same in general line variations in the high-speed streams as well as to the coefficient K expressed by this way the diffusion coefficient of cosmic-rays. 相似文献
6.
H. Mavromichalaki V. Tritakis B. Petropoulos E. Marmatsouri A. Vassilaki A. Belehaki X. Raphios J. C. Noëns B. Pech 《Astrophysics and Space Science》1994,218(1):35-57
The analysis of the daily measurements of the coronal green and red line intensities as well as the K-corona brightness, which have been collected by the Pic-du-Midi Observatory, for the time period 1944–1974, has revealed some very interesting features. North-South (N-S) asymmetries for all these coronal intensities are confirmed again for this time period. The main point of this analysis is a strong evidence of longitudinal distribution of the coronal intensities as derived from the data record. In our effort to confirm this asymmetry, we have examined the yearly and monthly distribution of the asymmetry coefficient in each solar quadrant showing that the northeast (NE) quadrant appears the most active of all. We have also examined the intensity ratios measured at the East and West solar limbs which is continuously greater than the unit.A seasonal variation of this ratio has also been reported with a maximum during the winter period and a minimum during the summer period. 相似文献
7.
The domestic and industrial waste water from most of the greater Athens, Greece area is discharged into shallow water at the
upper end of the semi-enclosed Saronikos Gulf. The lack of circulation and excess organic matter has led to the formation
of a rapidly expanding sludge field. Black anoxic sediments high in organic carbon now cover almost 9 sq km of sea floor and
contain high concentrations of heavy metals. Maximum increases above background values range from 22× for mercury, 1500× for
arsenic, 1200× for chromium, to 3000× for zinc. The principal sources of metals are 1) a fertilizer factory, 2) the Athens
sewer outfall, and 3) the industries in eastern Elefsis Bay. 相似文献
8.
Cosmic-ray intensity data for the period 1964–1985 covering two solar cycles are used to investigate the solar activity behaviour in relation to cosmic-ray modulation. A detailed statistical analysis of them shows a large time-lag of about one and half years between cosmic-ray intensity and solar activity (as indicated by sunspot number, solar flares and high-speed solar-wind streams) during the 21st solar cycle appearing for a first time. This lag indicates the very high activity level of this solar cycle estimating the size of the modulating region to the unambiguous value of 180 AU. The account of the solar-wind speed in the 11-year variation significantly decreases the modulation region of cosmic-rays to the value of 40 AU.A comparison with the behaviour of the previous solar cycle establishes a distinction between even and odd solar cycles. This is explained in terms of different contributions of drift, convection and diffusion to the whole modulation mechanism during even and odd solar cycles. 相似文献
9.
A reference catalogue of 430 well-defined high-speed plasma streams detected in solar-wind observations from 1972 to 1984 is presented. We have given the main characteristics of the streams as the beginning time and the duration of the stream, the interplanetary magnetic field polarity, etc. We have also separated them with respect to their origin into two categories: the corotating and the flare-generated streams. As a first application of this useful catalogue, a correlative study between the maximum speed of streams and the A
p
-index of geomagnetic activity is carried out. 相似文献
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