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1.
V. K. Verma 《Journal of Astrophysics and Astronomy》2000,21(3-4):173-176
We report here a study of various solar activity phenomena occurring in both north and south hemispheres of the Sun during
solar cycles 8–23. In the study we have used sunspot data for the period 1832–1976, flare index data
for the period 1936-1993, Hα flare data 1993–1998 and solar active prominences data for the period 1957–1998.
Earlier Verma reported long-term cyclic period in N-S asymmetry and also that the N-S asymmetry of solar activity phenomena
during solar cycles 21, 22, 23 and 24 will be south dominated and the N-S asymmetry will shift to north hemisphere in solar
cycle 25. The present study shows that the N-S asymmetry during solar cycles 22 and 23 are southern dominated as suggested
by Verma. 相似文献
2.
A study of the green corona rotation rate, during the period 1970–1974, confirms that the differential rotation degree varies systematically through a solar cycle and that the corona rotates in an almost rigid manner before sunspot minimum. During the first two years, 1970–1971, the differential rotation degree, characteristic of high solar activity periods is detected. While during the years of declining activity, 1972–1974, a drastic decrease of the differential rotation degree occurs and the green corona rotates almost rigidly, as the coronal holes observed in the same period. These conclusions are valid only for the rotation of coronal features with lifetime of at least one solar rotation. 相似文献
3.
Different records of solar activity (Wolf and group sunspot number, data on cosmogenic isotopes, historic data) were analyzed by means of modern statistical methods, including one especially developed for this purpose. It was confirmed that two long-term variations in solar activity – the cycles of Gleissberg and Suess – can be distinguished at least during the last millennium. The results also show that the century-type cycle of Gleissberg has a wide frequency band with a double structure consisting of 50–80 years and 90–140 year periodicities. The structure of the Suess cycle is less complex showing a variation with a period of 170–260 years. Strong variability in Gleissberg and Suess frequency bands was found in northern hemisphere temperature multiproxy that confirms the existence of a long-term relationship between solar activity and terrestial climate. 相似文献
4.
The cosmic-ray 1.68-year variation: A clue to understand the nature of the solar cycle? 总被引：1，自引：0，他引：1
Using the maximum entropy method (MEM), the cosmic-ray power spectral density in the frequency range 3 × 10–9–2 × 10–7 Hz has been estimated for the period 1947–1990. Cosmic-ray intensity data were integrated from the ion chamber at Huancayo and the neutron monitor at Deep River, following the method of Nagashima and Morishita (1980). The estimated spectrum shows power-law dependence (f
–1.62), with several peaks superimposed. Periodicities of the different peaks are identified and related to solar activity phenomena; most of them were reported in the past. Once the 11-yr variation is eliminated, the most prominent feature in the spectrum is a variation, not reported before, with a period of 1.68 yr (604.8 d). This peak is correlated with fluctuations of similar periodicities found in the southern coronal hole area and in large active regions. The importance that this variation may have to elucidate the solar magnetic flux emergence and the activity cycle is discussed.Deceased 10 April, 1995. 相似文献
5.
In this paper we have examined the real behaviour of solar activity during the period AD 1400–1600. The results are as follows: (1) the distributions of the 20 naked-eye sunspot records are inhomogeneous. There are 2 sightings in the 15th century and 18 sightings in the 16th century; (2) the distributions of auroral records are similar to sunspot. There are 33 records in the 15th century and 315 records in the 16th century; (3) the climatic fluctuations in China shows that the period AD 1430–1520 was cold while the period AD 1520–1620 was warm. These facts clearly demonstrate that the Spörer Minimum, if it extended from AD 1460 to 1550, could be a specious results and it, if its extent was AD 1400–1510, is a real feature of solar variability in that time.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984. 相似文献
6.
We present the behaviour of the coronal index (CI) of solar activity over the period 1986–(May) 1996. These data are not only a good tool for studying the activity of the Sun as a star, but they also represent an invaluable source of information in our quest to understand the properties of the heliosphere as a whole. Having compared the variations of CI and of the solar 0.05–0.8 nm soft X-ray flux over the period 1986–1995 we did not find any significant correlation between the two quantities. This favours a scenario in which the sources of the soft X-ray flux are small-scale regions of the corona, and processes of both ionization and recombination do not occur in the same volume of the solar corona as for the green corona. 相似文献
7.
In the 19th century De la Rue, Stewart, and Loewy carried out a compilation of drawings and photographs of the solar sunspots in the period 1832–1868. From these drawings and photographs, they determined fortnightly values of the sunspot areas. In this work, monthly values of the sunspot areas for the period 1832–1868 are calculated and the reliability of these data in terms of the solar activity indices is discussed. 相似文献
8.
Periodicities of 22, 8 and 6 years have been found by a statistical analysis of the coefficient of atmospheric activity R of Jupiter for the time period 1910–1985.We have also found variations of the coefficient of asymmetry of the activity Z measured by the Observatory of Athens for the time period 1956–1985 with periodicities of 12, 8, 6 and 4 years by statistical analysis.The same periodicities have been recently found in an analysis of the total number of solar flares and in the number of high velocity solar wind streamers. 相似文献
9.
The analysis of the daily measurements of the coronal green line intensity, which have been extensively tested for homogeneity and freedom of trends observed at the Pic-du-Midi observatory during the period 1944–1974, has revealed some characteristic asymmetric variations. A north-south asymmetry of the green line intensity is the main feature of the period 1949–1971 while a south-north one is obvious within 1972–1974 and the minor statistical significance span 1944–1948. On the other hand a significant W-E asymmetry has been confirmed in the whole period 1944–1974. It is noteworthy that the period 1949–1971, where the N-S asymmetry takes place consists a 22-yr solar cycle which starts from the epoch of the solar magnetic field inversion of the solar cycle No. 18 and terminates in the relevant epoch of the cycle No. 20.The combination of N-S and S-N asymmetry with a W-E one makes the NW solar-quarter to appear as the most active of all in the 22-yr cycle 1949–1971, while in the periods 1944–1948 and 1972–1974 the SW quarter is the most active. Finally, from the polar distribution of the green line intensity has been derived that the maximum values of the asymmetries occur in heliocentric sectors ± 10°–20° far from the solar equator on both sides of the central meridian.Physical mechanisms which could contribute to the creation of both N-S and E-W asymmetries of the solar activity and the green line intensity as an accompanied event, like different starting time of an 11-yr solar cycle in the two solar hemispheres, the motion of the Sun towards the Apex, and short-lived active solar longitudes formed by temporal clustering of solar active centers, have been discussed. 相似文献
10.
R. K. Srivastava 《Astrophysics and Space Science》1986,124(2):397-402
The new period (P=0
.
d
461700) of the eclipsing binary system DX Aqr has been presented, which is based on available times of minima. O–C diagram of DX Aqr has been presented for the first time, and the period variations present in the system have been analysed. In all five period increases and five period decreases are nothed, and four period increases and five period decreases have been discussed. The strongest period increase occurs between 1975 and 1976. The total period change in different portions of the O–C diagram ranges from 1.40×10–4 d to 3.61×10–6 d. Appreciable period fluctuations have been noted to have occurred in the time intervals, 1964–1965 and 1974–1975. 相似文献
11.
Daily calcium plage areas for the period 1951–1981 (which include the solar cycle 19 and 20) have been used to derive the rotation period of the Sun at latitude belts 10–15 ° N, 15–20 ° N, 10–15 ° S, and 15–20 ° S and also for the entire visible solar disk. The mean rotation periods derived from 10–20 ° S and N, total active area and sunspot numbers were 27.5, 27.9, and 27.8 days (synodic), respectively. A power spectral analysis of the derived rotation rate as a function of time indicates that the rotation rate in each latitude belt varies over time scales ranging from the solar activity cycle, down to about 2 years. Variations in adjacent latitude belts are in phase, whereas those in different hemispheres are not correlated. The rotation rates derived from sunspot numbers also behave similarly though the dependence over the solar cycle are not very apparent. The total plage areas, integrated over the entire visible hemisphere of the Sun shows a dominant periodicity of 7 years in rotation rate, while the other time scales are also discernible. 相似文献
12.
Observations of solar radio emission at 3 cm wavelength have been made at Japal-Rangapur Observatory for 1980–1981, the solar maximum year using the 3 m radio telescope. The correlation between microwave solar emissions and the sunspot activity on monthly basis has been found to be high during the maximum phase and in the high cm wavelength band. The basic component has been estimated statistically for successive solar rotations using the data obtained at Japal-Rangapur Observatory. Further, this was compared with the data obtained at other cm wavelengths during 1980–1981 and the solar minimum period 1975–1976 of the 21st cycle. The comparison showed pronounced dips in flux levels at different wavelengths during the summer months of the solar maximum year which may be attributed to the presence of coronal holes in the various levels of the solar atmosphere. The computed basic component values showed pronounced variation at high cm wavelengths for the solar maximum period with dissimilar variations at different wavelengths. During the solar minimum period the variations were negligibly small and showed more or less constant level of activity.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984. 相似文献
13.
We examine the `Group' sunspot numbers constructed by Hoyt and Schatten to determine their utility in characterizing the solar activity cycle. We compare smoothed monthly Group sunspot numbers to Zürich (International) sunspot numbers, 10.7-cm radio flux, and total sunspot area. We find that the Zürich numbers follow the 10.7-cm radio flux and total sunspot area measurements only slightly better than the Group numbers. We examine several significant characteristics of the sunspot cycle using both Group numbers and Zürich numbers. We find that the `Waldmeier Effect' – the anti-correlation between cycle amplitude and the elapsed time between minimum and maximum of a cycle – is much more apparent in the Zürich numbers. The `Amplitude–Period Effect' – the anti-correlation between cycle amplitude and the length of the previous cycle from minimum to minimum – is also much more apparent in the Zürich numbers. The `Amplitude–Minimum Effect' – the correlation between cycle amplitude and the activity level at the previous (onset) minimum is equally apparent in both the Zürich numbers and the Group numbers. The `Even–Odd Effect' – in which odd-numbered cycles are larger than their even-numbered precursors – is somewhat stronger in the Group numbers but with a tighter relationship in the Zürich numbers. The `Secular Trend' – the increase in cycle amplitudes since the Maunder Minimum – is much stronger in Group numbers. After removing this trend we find little evidence for multi-cycle periodicities like the 80-year Gleissberg cycle or the two- and three-cycle periodicities. We also find little evidence for a correlation between the amplitude of a cycle and its period or for a bimodal distribution of cycle periods. We conclude that the Group numbers are most useful for extending the sunspot cycle data further back in time and thereby adding more cycles and improving the statistics. However, the Zürich numbers are slightly more useful for characterizing the on-going levels of solar activity. 相似文献
14.
Power spectral analysis of cosmic-ray intensity recorded by eight stations was carried out over a wide range of frequencies from 2.3 × 10–8 Hz to 5.8 × 10–6 Hz (2–500 days) during the period 1964–1995. Spectrum results of large-scale fluctuations have revealed the existence of a broad peak near 250–285 days and a narrower peak at 45–50 days during the studied epochs as a stable feature in all neutron monitors covering a wide rigidity range. The cosmic-ray power spectrum displayed significant peaks of varying amplitude with the solar rotation period (changed inversely with the particle rigidities) and its harmonics. The amplitudes of 27-day and 13.5-day fluctuations are greater during the positive-polarity epochs of the interplanetary magnetic field (qA>0) than during the qA<0 epochs. The comparison of cosmic-ray power spectra during the four successive solar activity minima have indicated that at the low-rigidity particles the spectrum differences between the qA>0 and qA<0 epochs are significantly large. Furthermore, the spectrum for even solar maximum years are higher and much harder than the odd years. There are significant differences in the individual spectra of solar maxima for different cycles. 相似文献
15.
A New Solar Broadband Radio Spectrometer (SBRS) in China 总被引：1，自引：0，他引：1
Qijun Fu Huirong Ji Zihai Qin Zhicai Xu Zhiguo Xia Hongao Wu Yuying Liu Yihua Yan Guangli Huang Zhijun Chen Zhenyu Jin Qijun Yao Congling Cheng Fuying Xu Min Wang Libei Pei Shanhuai Chen Guo Yang Chenming Tan Suobiao Shi 《Solar physics》2004,222(1):167-173
A new radio spectrometer, Solar Broadband Radio Spectrometer (SBRS) with characteristics of high time resolution, high-frequency resolution, high sensitivity, and wide frequency coverage in the microwave region is described. Its function is to monitor solar radio bursts in the frequency range of 0.7–7.6 GHz with time resolution of 1–10 ms. SBRS consists of five `component spectrometers' which work in five different wave bands (0.7–1.5 GHz, 1.0–2.0 GHz, 2.6–3.8 GHz, 4.5–7.5 GHz, and 5.2–7.6 GHz, respectively). A combination of multi-channel and scanning techniques is adopted. The component spectrometers are attached to different antennas which are separately located at Beijing, Kunming, and Nanjing. Close attention was paid to solve the problems of sensitivity, dynamic range, interference-resistance, data acquisition, and handling a large amount of data. The SBRS was put into operation in the 23th solar maximum activity period, and has proved itself to be a valuable instrument for the study of solar bursts in microwaves. 相似文献
16.
The rotation characteristics of large-scale (global) magnetic fields (GMF) and their relation to the activity of local fields (LMF) are studied over a long time interval (1915–1996). The main results are as follows. The GMF rotation rates and LMF activity vary in anticorrelation. Both variations have similar periods (11 years and a quasi-secular period of about 55–60 years), but are shifted relative to each other by half an 11-year cycle. Therefore, (1) the GMF rotation rate increases at the minimum of the 11-year cycle of LMF activity. (2) The GMF rotation rate is faster in the less active hemisphere. (3) The GMF rotation period slows down at the maximum of the secular LMF activity (cycles 18 and 19). 相似文献
17.
R. K. Srivastava 《Astrophysics and Space Science》1987,132(2):331-335
The O–C diagram of the eclipsing binary GG Cassiopeiae has been presented for the first time, and the period changes present in the system have been analysed. In all three period changes are noted. The strongest period change has been found to occur in the time-interval 1942 to 1966. The total period change in different portions of the O–C diagram ranges from 7.1×10–7 d to 2.0×10–5 d. The stronger period changes appear to have occurred after 1942; prior to it, the system has shown a negligible period change. The overall picture of the O–C diagram suggests that the O–C values of the system GG Cas are negative after 1942. The presence of a third body does not appear probable. The period fluctuations are also appreciable. A new period (P=3
.
d
758733) has been presented. 相似文献
18.
The structure of time series of daily global indices of solar activity is investigated: the sunspot numbers for the time interval between the years 1854 and 1996, the Greenwich total sunspot area for 1874–1983, the radio-flux at 10.7 cm (F10.7) for 1964–1996, and the Stanford mean solar magnetic field for 1975–1996. The fractal dimensions are determined by two fractal and spectral methods. The identified three time-scale ranges, 2 days–2 months, 2 months–2 years, 2 years–8 and more years, with the fractal dimensions 1.4–1.6, 2, 1.2–1.6, respectively, show perhaps some fractal structure of time series of global indices. The first time-scale range may correspond to ordinary brownian noise and the second to flicker noise. The solar rotation influence of the value of the fractal dimensions at the time range close to the rotational period is studied. 相似文献
19.
Hari Om Vats 《Solar physics》1992,138(2):379-386
Characteristics of flare-associated high-speed solar plasma streams are investigated using measurements from space probes and Earth-orbiting spacecraft for the period 1964–1982. The maximum observed velocity (V
m) of these streams range from 400 to 850 km s–1} with peak probability for 600 km s–1}. These remain for the period of 1–10 days with the peak occurrence 3 days. The difference between the pre-stream velocity (V
0) and the maximum velocity (V
m) of any high-speed stream serves as the measure of its intensity. For about 60% of the flare associated streams, (V
m-V
0) is well in excess of 200 km s–1} and in some cases becomes as large as 450 km s–1}. The yearly percentage occurrence, total duration and the product of mean (V
m - V
0) with total duration of the high-speed streams during the year correlates well with solar activity, e.g., maximum during high solar activity period and minimum during low solar activity. The study suggests that presence of sunspots plays a significant role in the generation of flare associated high-speed solar streams. 相似文献
20.
Prominences, in contrast to other solar activity features, may appear at all heliographic latitudes. The position of zones where prominences are mainly concentrated depends on the cycle phase of solar activity. It is shown, for prominence observations made at Lomnický tít over the period 1967–1996, how the position of prominence zones changes over a solar cycle, and how these zones could be connected with other solar activity features. Our results obtained could be an additional source to do a better prediction of solar activity. Time-latitudinal distribution is also shown for the green corona (Fexiv, 530.3 nm). Distribution of the green coronal maxima shows that there are equator-migrating zones in the solar corona that migrate from latitudes of 45° (starting approximately 2–3 years after the cycle start) to higher latitudes 70°, and then turn (around the cycle maximum) towards the equator, reaching the equator in the next minimum (this duration lasts 18–19 years). Polar branches separate from these zones at the cycle minimum (2–3 years before above-mentioned zones) at latitudes of 50°, reaching the poles at the maximum of the present cycle. The picture becomes dim when more polar prominence zones are observed. Prominences show both the poleward and equatorward migration. Comparison between both solar activity features is also discussed. 相似文献