共查询到20条相似文献，搜索用时 25 毫秒
1.
Howard C. McAllister 《Solar physics》1974,34(1):3-10
The rotation of the solar corona has been studied using recurrence properties of the green coronal line (5303 Å) for the interval 1947–1970. Short-lived coronal activity is found to show the same differential rotation as short-lived photospheric magnetic field features. Long-lived recurrences show rigid rotation in the latitude interval ±57°.5. It is proposed that at least part of the variability of rotational properties of the solar atmosphere may be understood as a consequence of coexistence of differential and rigid solar rotation.On leave from Torino University, Italy, as an ESRO-NASA Fellow. 相似文献
2.
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
3.
L.H. Ma 《New Astronomy》2009,14(1):1-3
Long-term variations of solar activity significantly affect terrestrial phenomena. Studies have shown cyclic components in solar activity and geophysical phenomena (e.g., the Schwabe, Hale, Gleissberg, and Suess cycles, and a cycle of about 2300 years). In this paper, the wavelet technique is employed to investigate the Gleissberg cycle in solar variations during 5000 BC–1995 AD. Analysis shows time-variable characteristics in the Gleissberg solar cycle over the period; no obvious correlation between the Gleissberg and Suess cycles has been found. 相似文献
4.
A study has been made of the yearly variation of the cosmic ray intensity for the years 1961–67 inclusive using pressure corrected neutron monitor data from both hemispheres to minimize seasonal meteorological effects. An annual wave is found in the data with an amplitude which varied between 0.2 and 1.0 per cent during the period but which had a sensibly constant phase, the time of maximum being in March. These observations, which are shown to be consistent with the observed heliolatitude distribution of coronal 5303Å emission, indicate the existence of a southerly directed asymmetrical gradient of up to 8 per cent perpendicular to the solar equatorial plane. It is found that the cosmic ray intensity at the Earth is controlled by the solar activity in a narrow band of heliolatitudes ±10° or ±20° centred at the heliolatitude of the Earth. Also, the results indicate that there was a phase lag of 1 ± 1 month between solar activity and the resulting changes in the cosmic ray intensity at the Earth giving a radius for the modulating region of ? 10 A.U. during the period of low solar activity considered. 相似文献
5.
Elena E. Benevolenskaya 《Solar physics》1998,181(2):479-489
The longitudinal structure of the double magnetic cycle of solar activity has been investigated using Stanford magnetograph data from 1976 to 1996 (cycles 21 and 22). It is shown that both high-frequency and low-frequency sources of the magnetic field are present in the data and that they reach their maxima in longitudinal zones that are separated by 20°. Some longitudinal zones are found to exist in which the high-frequency component is dominant and other longitudinal zones are found in which the low-frequency component is dominant. 相似文献
6.
A non-linear coupling function between sunspot maxima and aa minima modulations has been found as a result of a wavelet analysis of geomagnetic index aa and Wolf sunspot number yearly means since 1844. It has been demonstrated that the increase of these modulations for the past 158 years has not been steady, instead, it has occurred in less than 30 years starting around 1923. Otherwise sunspot maxima have oscillated about a constant level of 90 and 141, prior to 1923 and after 1949, respectively. The relevance of these findings regarding the forecasting of solar activity is analyzed here. It is found that if sunspot cycle maxima were still oscillating around the 141 constant value, then the Gnevyshev–Ohl rule would be violated for two consecutive even–odd sunspot pairs (22–23 and 24–25) for the first time in 1700 years. Instead, we present evidence that solar activity is in a declining episode that started about 1993. A value for maximum sunspot number in solar cycle 24 (87.5±23.5) is estimated from our results. 相似文献
7.
Intermediate-term periodicities in solar activity 总被引：2，自引：0，他引：2
The presence of intermediate-term periodicities in solar activity, at approximately 323 and 540 days, has been claimed by different authors. In this paper, we have performed a search for them in the historical records of two main indices of solar activity, namely, the daily sunspot areas (cycles 12–21) and the daily Zürich sunspot number (cycles 6–21). Two different methods to compute power spectra have been used, one of them being especially appropriate to deal with gapped time series. The results obtained for the periodicity near 323 days indicate that it has only been present in cycle 21, while in previous cycles no significant evidence for it has been found. On the other hand, a significant periodicity at 350 days is found in sunspot areas and Zürich sunspot number during cycles 12–21 considered all together, also having been detected in some individual cycles. However, this last periodicity must be looked into with care due to the lack of confirmation for it coming from other features of solar activity. The periodicity around 540 days is found in cycles 12, 14, and 17 in sunspot areas, while during cycles 18 and 19 it is present, with a very high significance, in sunspot areas and Zürich sunspot number. It also appears at 528 days in sunspot areas during cycles 12–21. On the other hand, it is important to note the coincidence between the asymmetry, favouring the northern hemisphere, of sunspot areas and solar flares during cycle 19, and the fact that the periodicity at 540 days was only present, with high significance, in that hemisphere during that solar cycle. 相似文献
8.
X-ray photographs obtained with a zone plate camera on October 3, 1967 in the wavelength band 49.5–52.5 Å have been investigated photometrically.The most intense X-ray emission corresponds with active regions in H and Ca ii. About one quarter of the total solar flux is emitted by the three brightest X-ray sources (A, E and J). X-ray emission from quiet regions is also observed. Limb brightening is found, also at the poles, which indicates a higher electron density at the poles than during solar minimum.The brightest X-ray regions have a very small core of the order of 20. No relation to magnetic field strengths of sunspots has been found. However, a correlation with active prominences cannot be ruled out. X-ray source A is related either to prominence activity or to flare activity. One X-ray region (J) is probably related to flare activity.Assuming an electron temperature of 3 × 106K to 5 × 106K for coronal active regions an emission measure of a few times 1049 cm–3 is derived, which yields an electron density of a few times 1010 cm–3. 相似文献
9.
Mustafa önal 《Earth, Moon, and Planets》1988,43(2):107-115
The positions of the 13588 sunspot groups observed during the cycle of 1950–1960 at the Istanbul University Observatory have been corrected for the effect of differential rotation. The evolution probability of a sunspot group to the other one in the same region have been determined. By using the Markov chain approximation, the types of these groups and their transition probabilities during the following activity cycle (1950–1960), and the concentration of active regions during 1950–1960 have been estimated. The transition probabilities from the observations of activity cycle 1960–1970 have been compared with the predicted transition probabilities and a good correlation has been noted. 相似文献
10.
L. A. Plyusnina 《Solar physics》2010,261(2):223-232
There are two types of active longitudes (ALs) in terms of the distribution of sunspot areas: long-lived and intra-cyclic
ALs. The rotation period of the long-lived ALs has been determined by a new method in this paper. The method is based on the
property of ALs to be maintained over several cycles of solar activity. The daily values of sunspot areas for 1878 – 2005
are analyzed. It is shown that the AL positions remain almost constant over a period of about ten cycles, from cycle 13 to
cycle 22. The rotation period was found to be 27.965 days during this period. The dispersion in AL positions is about 26°
from cycle to cycle, which is half of the dispersion observed in the Carrington system. The ALs in the growth phase of the
activity cycle are more stable and pronounced. The excess in solar activity in the ALs over adjacent longitudinal intervals
is about 12 – 14%. It is shown that only one long-lived AL can be observed at one time on the Sun, as a rule. 相似文献
11.
An analysis of monthly data from nine world-wide neutron monitoring stations over the period 1965–1975 is carried out for the study of the long-term cosmic-ray modulation. In an attempt to gain insight into the relationships which exist between solar activity, high-speed solar wind streams and various terrestrial phenomena an empirical relation for the cosmic-ray modulation has been found. Accordingly the modulated cosmic-ray intensity is equal to the galactic cosmic-ray intensity corrected by a few appropriate solar, interplanetary and terrestrial activity indices which causes the disturbances in interplanetary space, multiplying with the corresponding time-lag of cosmic-ray intensity from each of these indices. This relation is well explained by a generalization of the Simpson solar wind model which has been proved by the spherically symmetric diffusion-convection theory. 相似文献
12.
We have selected observations of quiet K corona in maximum activity phase (1970 and 1972) and we have computed the corresponding density models. The density is found to be two times smaller than in average maximum coronal models (Newkirk, 1967) and nearly equal to that of minimum coronas (Saïto, 1970). The research of quiet coronas between active periods has been extended to the three past solar cycles thanks to 5303 Å measurements: very low 5303 Å intensities, corresponding to very small densities, are found even in maximum activity phase. A short discussion about the values of average quiet coronal models is given. 相似文献
13.
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
14.
The change in the darkness of the Great Red Spot (GRS) of Jupiter (1894–1974) has been analysed with Fourier (FFT), Maximum Entropy and Power spectrum (Blackman-Tukey window) (PSA) methods of spectrum analysis. Significance, non-randomness and stationarity tests assigned high variance to periodicities of 33 ± 4, 13–15, about 11, 9 and 3 yrs. The highest correlation between solar activity and GRS darkness was found for the 14th and 16th solar cycle. The periodicities obtained are interpreted as the combined eftects of solar activity, planetary resonances and internal jovian mechanisms. 相似文献
15.
Analyzing daily values of the total solar irradiance (TSI), the coronal index of solar activity (CI), and the Mg II 280-nm
core-to-wing ratio (Mg II index), we have found that the temporal variations of these indices are very similar to each other
during the period from 1978 to 2005. The correlation between CI and TSI, with the PSI correction lying within the interval
under study, has been found to be 0.699, which is very close to the value of 0.703 of the correlation between Mg II and TSI
for 27-day averages (the CI – Mg correlation is 0.824). The regression equation between CI and TSI is almost linear, except
for TSI depletions when a large number of sunspots are present on the visible disk. By employing CI, an extrapolation of TSI
back to 1947 is presented. 相似文献
16.
17.
More than 600 double-station photographic recordings of Perseid meteor trails have been obtained at various stations in the period 1937–1985. This large data sample has recently been used to determine the activity profile and mean orbit of the Perseid meteoroid stream (Lindblad and Poruban, 1994). In the present paper the radiant of the Perseid meteoroid stream is studied based on a sample of 592 double-station photographic recordings. The daily motion of the radiant and the change of the size of the radiant area with date is investigated. A daily motion of 1.40° in right ascension and 0.20° in declination is derived. These values are slightly larger than those previously found by other researchers. The contraction of the radiant area at shower maximum previously reported from visual observations is confirmed. In a further study radiant areas derived for the dates of the new and the old Perseid maxima are compared. It is found that the radiant area of the new maximum is smaller than that of the old maximum. 相似文献
18.
R. Sh. Natsvlishvili 《Astrophysics》1999,42(1):117-118
Flare periodicity has been found in the flare star Pleiades No. 484. The period of its flare activity is determined from an
analysis of the flares’time distribution.
Translated from Astrofizika, Vol. 42, No. 1, pp. 159–160, January–March, 1999. 相似文献
19.
In the present work, the phase relation between activities of solar active prominences respectively at low and high latitudes in the period 1957–1998 has been studied. We found that from the solar equator to the solar poles, the activity of the solar active prominences occurs earlier at higher latitudes, and that the cycle of the solar active prominences at high latitudes (larger than 50°) leads by 4 years both the sunspot cycle and the corresponding cycle of the solar active prominences at low latitudes (less than 40°). 相似文献
20.
The high/low-amplitude anisotropic wave train events (HAE/LAE) in CR intensity have been investigated during the period 1981–1990, using the neutron monitoring data for different latitudes. In all, 21 HAE and 15 LAE cases have been studied. It has been observed that the phase of the diurnal anisotropy remains in the same co-rotational direction for the majority of the HAE/LAE cases. However, it has also been observed that the phase of the diurnal anisotropy changes to later hours in some of the HAE cases, whereas it changes to early hours in some of the LAE cases. Further, the amplitude of the semi-diurnal anisotropy for HAE/LAE cases remains statistically the same; however, the phase of the semi-diurnal anisotropy for HAE has been found to shift to later hours for all events. Furthermore, the HAE occur dominantly during the declining phase of solar activity, whereas LAE occur dominantly during the minimum solar activity period. The geomagnetic activity index-Ap has been observed to remain low during the period of each HAE/LAE. The possible phenomenon to cause the enhanced/low-amplitude daily variation has been proposed to appear on the back side of the Sun. 相似文献