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1.
The average rate of growth during the ascending portion of the sunspot cycle, defined here as the difference in smoothed sunspot number values between elapsed time (in months) t and sunspot minimum divided by t, is shown to correlate (r 0.78) with the size of the sunspot cycle, especially for t 18 months. Also, the maximum value of the average rate of growth is shown to highly correlate (r = 0.98) with the size of the cycle. Based on the first 18 months of the cycle, cycle 22 is projected to have an R(M) = 186.0 ± 27.2 (at the ± 1 level), and based on the first 24 months of the cycle, it is projected to have an R(M) = 201.0 ± 20.1 (at the ± 1 level). Presently, the average rate of growth is continuing to rise, having a value of about 4.5 at 24 months into the cycle, a value second only to that of cycle 19 (4.8 at t = 24 and a maximum value of 5.26 at t = 27). Using 4.5 as the maximum value of the average rate of growth for cycle 22, a lower limit can be estimated for R(M); namely R(M) for cycle 22 is estimated to be 164.0 (at the 97.5% level of confidence). Thus, these findings are consistent with the previous single variate predictions that project R(M) for cycle 22 to be one of the greatest on record, probably larger than cycle 21 (164.5) and near that of cycle 19 (201.3).  相似文献   

2.
Finsterle  W.  Fröhlich  C. 《Solar physics》2001,200(1-2):393-406
Several candidates for low-order p modes (n 5) and possibly g modes were found by applying mode-detection techniques such as multivariate spectral regression analysis and time-frequency analysis to the VIRGO full-disc solar irradiance data. Three out of the candidates for low-order p modes could be confirmed by significant peaks in the un-treated power spectra in good agreement with theoretical predictions. The frequency of a fourth candidate for a low-order p mode lies some 2.8 Hz below the predicted frequency. The candidates found for g modes are less reliable, since none of them could be confirmed neither by significant peaks in the un-treated power spectra nor by the detection of multiplets.  相似文献   

3.
CS(J=1–0), C34S(J=1–0), and CH3OH(10–00A and E) emission lines in the core region of molecular cloud associated with NGC 7538 have been surveyed at angular resolution of 33. Distribution of CS column density shows two prominent peaks. Both blue and red wings in CS line are most prominent at 30 northwest of IRS 11.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.This work was carried out under the common use observation program at the Nobeyama Radio Observatory (NRO). NRO, a branch of the Tokyo Astronomical Observatory, University of Tokyo, is a cosmic radio observing facility open to outside users.  相似文献   

4.
Intensity observations of solarp modes are needed to form a complete picture of wave propagation in the photosphere. Ground-based intensity observations are severely hampered by terrestrial atmospheric noise. Partial cancellation of the noise power can be achieved if two spectra having disparate signal-to-noise ratios, and based on time series acquired simultaneously at the same site, are combined. A method of combining the spectra is suggested in which one amplitude is scaled and subtracted from the other. The result is squared yielding a positive-definite power density. To test the method, the intensity of light scattered by the Earths atmosphere was recorded at fifteen-second intervals in two narrow bands centered on 0.5 and 1.6. When the two resulting spectra were combined, the noise power was attenuated by a factor of 2.7. The scale factor was varied about its optimum value, revealing that noise peaks have a different signature than signal peaks, and opening up the possibility of a new tool in discrimination against noise peaks. Maxima at symmetry-allowed frequencies and minima at symmetry-forbidden frequencies indicate that the probability that these results are obtained by chance is only 6.1 × 10–4. The positions of these maxima and minima also support the solar-cycle dependent frequency shifts found by Pallé, Régulo, and Roca Cortés (1990a).  相似文献   

5.
Perpendicular diffusion due to either field line wandering or random gradient and curvature effects makes a substantial contribution to the radial transport of particles at distances of about 5 AU and beyond when lines of the interplanetary magnetic field (IMF) become almost azimuthal. Here test particle trajectories are followed in a field model which uses a magnetic field sample taken by Voyager 2 at 14.8 AU. Techniques previously developed (Moussas et al., 1982a) are employed to calculate the perpendicular diffusion coefficient for 100 MeV protons and arising from random gradient and curvature effects. The result K=(2.8±0.9)×1021 cm2 s–1 shows a substantial increase above the value determined previously at 5 AU and, assuming a power law radial dependence Kr , implies 0.8–1.1. This result is consistent with observations of the cosmic-ray radial gradient.  相似文献   

6.
COMPTEL on board CGRO has observed a very strong (S[> 0.3 MeV] = 2.03 × 10–4 erg cm–2), complex, and long lasting (162 s) gamma-ray burst on February 17, 1994 (GRB 940217). Temporal fluctuations occur on timescales as short as 100 ms. Hard-to-soft spectral evolution has been observed during the burst emission and also within individual peaks. The photon spectra obtained within the 6 peaks can be modelled by single power law spectra and by broken power laws with break energies at around 1 MeV. The best-fit power law slopes vary between 1.1 and 3.5 throughout the event. The burst is located at [ 2000, 2000] = [29.5°, 3.8°] with a 3 error radius of 0.9°. COMPTEL does not detect any significant post-burst emission (as reported by EGRET) at low energies (< 30 MeV), and our upper limits are marginally consistent with the EGRET detections. Using high energy spectral and temporal information, distance limits to GRB 940217 have been derived.  相似文献   

7.
Photographic observations of the mean H and K profiles are given for several positions across the solar disk (0.1 < < 0.6). The core profiles of H and K are nearly identical at the same position on the sun.Estimates of the mean Doppler width and the depth of formation of the K2 emission peaks are given. A more elaborate analysis confirms that the K2 peaks are formed in a relatively shallow layer ( 0 3) in which the Doppler width decreases rapidly inward. The relevance of these conclusions to current attempts to predict theoretically the H and K profiles is discussed.  相似文献   

8.
El-Borie  M.A. 《Solar physics》2002,208(2):345-358
The ultra-low frequency power spectra (from 1 nHz to 10 Hz) for the solar wind ion density (N) and speed (SWS) measurements taken near 1 AU, have been examined during the period 1973–2000. Although the spectrum shows remarkable peaks at the wavelengths 0.5, 0.7, 1.0, 1.3 years, additional significant peaks of 2.6 yr and 5.6 yr for N and 9.6 yr for SWS are also found. Possible causes are discussed. The 9.6-yr period is not related to the period of the solar activity cycle, but there is some indication of an association with the coronal hole variations in the southern hemisphere of the Sun. The averages of solar wind ion density showed a periodic variation with three nearly equal peaks at intervals of 5.1±0.2 yr. The long-term enhancements in SWS reflect nearly stable variations and a continuously-existing feature in the heliosphere. The observed long periodicities in both N and SWS spectra may be strongly related to, or organized by, the observed variations in the coronal hole areas between northern and southern hemispheres of the Sun. The timing of the maximum peaks in solar ion densities and speeds spectrum is predicted.  相似文献   

9.
We describe a method for the analysis of magnetic data taken daily at the Vacuum Telescope at Kitt Peak. In this technique, accurate position differences of very small magnetic features on the solar surface outside active regions are determined from one day to the next by a cross-correlation analysis. In order to minimize systematic errors, a number of corrections are applied to the data for effects originating in the instrument and in the Earth's atmosphere. The resulting maps of solar latitude vs central meridian distance are cross-correlated from one day to the next to determine daily motions in longitude and latitude. Some examples of rotation and meridional motion results are presented. For the months of May 1988 and October–November 1987, we find rotation coefficients A = 2.894 ± 0.011, B = - 0.428 ± 0.070, and C = -0.370 ± 0.077 in rad s–1 from the expansion = A + B sin2 + C sin4, where is the latitude. The differential rotation curve for this interval is essentially flat within 20 deg of the equator in these intervals. For the same intervals we find a poleward meridional motion a = 16.0 ± 2.8 m sec -1 from the relation v = a sin, where v is the line-of-sight velocity.Operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.  相似文献   

10.
Fourier analysis of the R. Davis group data has been carried out. A method of signal selection at small signal/noise ratio was suggested and significance levels of individual peaks in the spectrum were determined. The correlation coefficients of neutrino fluxes and some characteristics of solar activity were calculated. The analysis conducted allowed us to reveal three significant peaks in the spectral density of 37Ar production rate in Cl detector: 113.8, 55.6, and 26.6 months (with a ratio of 421). The probability of a random origin of these peaks is less than 4%.  相似文献   

11.
It has been found that sunspot cycles 10–21, represented by quarterly mean values of Zürich sunspot number, can be suitably described by the F-distribution density function provided it is modified by introducing five characteristic parameters, in order to achieve an optimal fitting of each cycle. The average cycle calculated from cycles 10–21 has been used as a basis to forecast time and magnitude of the maximum of each cycle, as a function of various numbers of the first quarterly mean values in the beginning N = 8 to 16 quarters. The standard deviations at a 99% significance level calculated from the observed values depend on N, and vary from 1.6 to 1.1 quarters and 65 to 16 units of sunspot number. A rather sufficient forecast is obtained from N = 12 quarters (with inaccuracy of ± 1.5 quarters and ± 24 units); the forecast for cycle 22 yielded, for N = 12, the values t m = (15.4 ± 1.5) quarters ( 1990.I) and f(t m ) = (175 ±24 units).  相似文献   

12.
Using Greenwich data on sunspot groups during 1874–1976, we have studied the temporal variations in the differential rotation parametersA andB by determining their values during moving time intervals of lengths 1–5 yr successively displaced by 1 yr. FFT analysis of the temporal variations ofB (orB/A) shows periodicities 18.3 ± 3 yr, 8.5 ± 1 yr, 3.9 ± 0.5 yr, 3.1 ± 0.2 yr, and 2.6 ± 0.2 yr at levels 2. This analysis also shows five more periodicities at levels 1–2. The maximum entropy method is used to set narrower limits on the values of these periods. The reality of the existence of all these periodicities ofB (orB/A ) except the one at 2.8 yr is confirmed by analyzing the simulated time series ofB andB/A with values ofA andB randomly distributed within the limits of their respective uncertainties. Four of the prominent periods ofB agree, within their uncertainties, with the known periods in the the large-scale photospheric magnetic field. The deviations from the average differential rotation are larger near the sunspot minima. On longer time scales, the variations in the amount of sunspot activity per unit time are well correlated to the variations in the amplitudes of the torsional oscillation represented by the 22-yr periodicity inB. All the periods inB found here are in good agreement with the synodic periods of two or more consecutive planets. The possibility of planetary configurations providing perturbations needed for the Sun's MHD torsional oscillations is speculated upon and briefly discussed.  相似文献   

13.
A flare observed with the Hard X-Ray Imaging Spectrometer (HXIS) was studied during its rise to maximum temperature and X-ray emission rate. Two proximate flare loops, of lengths 2.8 × 109 cm and 1.1 × 1010 cm, rose to temperatures of 21.5 × 106 K and 30 × 106 K, respectively, in 30 s. Assuming equal heat flux F into each loop from a thermal source at the point where they met, we derive a simple relationship between temperature T and loop length , which gives a loop temperture ratio of 0.68, in close agreement with the observed ratio of 0.72. The observations imply that heating in each loop was maintained by a thermal flux of 5 × 109 ergs cm-2 s-1. It is suggested that conductive heating adequately describes the rise and maximum phase emissions in the loops and that long flare loops reach higher temperatures than short loops during the impulsive phase because of an equipartition of energy between them at their point of interaction.  相似文献   

14.
The large-scale photospheric magnetic field, measured by the Mt. Wilson magnetograph, has been analyzed in terms of surface harmonics (P n m )()cosm and P n m ()sinm) for the years 1959 through 1972. Our results are as follows. The single harmonic which most often characterized the general solar magnetic field throughout the period of observation corresponds to a dipole lying in the plane of the equator (2 sectors, n = m = 1). This 2-sector harmonic was particularly dominant during the active years of solar cycles 19 and 20. The north-south dipole harmonic (n = 1, m = 0) was prominent only during quiet years and was relatively insignificant during the active years. (The derived north-south dipole includes magnetic fields from the entire solar surface and does not necessarily correlate with either the dipole-like appearance of the polar regions of the Sun or with the weak polar magnetic fields.) The 4-sector structure (n = m = 2) was prominent, and often dominant, at various times throughout the cycle. A 6-sector structure (n = m = 3) occasionally became dominant for very brief periods during the active years. Contributions to the general solar magnetic field from harmonics of principal index 4 n 9 were generally relatively small throughout this entire solar cycle with one outstanding exception. For a period of several months prior to the large August 1972 flares, the global photospheric field was dominated by an n = 5 harmonic; this harmonic returned to a low value shortly after the August 1972 flare events. Rapid changes in the global harmonics, in particular, relative and absolute changes in the contributions of harmonics of different principal index n to the global field, imply that the global solar field is not very deep or that very strong fluid flows connect the photosphere with deeper layers.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

15.
We have detected 1.1 mm continuum emission from 24 of 53 Herbig Ae/Be stars surveyed with the JCMT. Survival analysis shows that 1.1 mm luminosity is correlated with bolometric luminosity and with IRAS 25µm luminosity. For those stars that were also detected at 0.45 or 0.8 mm we find a typical flux dependence of the form S #x03BD; 3, which is steeper than that of most classical T Tauri stars.  相似文献   

16.
Using optically identical telescopes at different sites, we have measured the solar diameter with a drift-scan technique. In order to investigate the cause of the observed fluctuations, we not only compare observations made simultaneously by different observers at the same telescope, but also observations made simultaneously at two different sites. Our main results are: (a) The mean error of a single drift time measurement is ±0.08s(or ± 1.1) at Izaña and ±0.11 s (or ± 1.7) at Locarno; this closely corresponds to the angular resolution at those two sites under normal seeing conditions, (b) We find no correlation between observations at different sites; a significant correlation exists, however, between observations made simultaneously by different observers at the same site: This indicates that most of the observed fluctuations are due to atmospheric effects (image motion) rather than personality effects, (c) The mean solar semi-diameter derived from a total of 1122 observations made in 1990 (472 at Izaña, 650 at Locarno) is R = (960.56 ± 0.03) (Izaña: 960.51, Locarno: 960.59); this may be compared with R = (960.32 ± 0.02) which is obtained from a re-analysis of 1773 observations made in 1981 (Izaña: 960.16, Locarno: 960.38). Although a small residual increase of the solar diameter during the last ten years seems to be indicated, we conclude that most - if not all - of the observed variations are due to variable seeing conditions, and that there is still no conclusive evidence for a genuine solar variation with amplitudes in excess of about ±0.3.  相似文献   

17.
We have used a 5.5 min time-sequence of spectra in the Fe i lines 5576 (magnetically insensitive), 6301.5 and 6302.5 (magnetically sensitive) to study the association of concentrated magnetic regions and velocity in the quiet Sun. After the elimination of photospheric oscillations we found downflows of 100–300 m s –1, displaced by about 2 from the peaks of the magnetic field; this velocity is comparable to downflow velocity associated with the granulation and of the same order or smaller than the oscillation amplitude. Quasi-periodic time variations of the vertical component of the magnetic field up to ± 40% were also found with a period near 250 s, close to the values found for the velocity field. Finally we report a possible association of intensity maxima at the line center with peaks of the oscillation amplitude.  相似文献   

18.
Two hyades giant stars, and Tau, have been studied from an analysis of strong line profiles. We get for Tau,T e =4750K and logg=2.7, and for Tau,T e =4700K and logg=2.8. Hydrogen-to-metal ratio for the two stars is nearly the same as that of solar value.  相似文献   

19.
We consider the problem of ion-acoustic wave generation, and resultant anomalous Joule heating, by a return current driven unstable by a small-area thick-target electron beam in solar flares. With a prescribed beam current evolution, j b (t) (and, therefore, a prescribed return current j p (t) = –j b (t)), and using an approximate local treatment with a two component Maxwellian plasma, and neglecting energy losses, we demonstrate the existence of two quite distinct types of ion-acoustic unstable heating regimes. First, marginally stable heating occurs when the onset of instability occurs at electron-ion temperature ratios T e /T i > 4.8. Secondly, there exists a catastrophic heating regime for which marginally stable evolution is impossible, when the onset of instability occurs at T e /T i < 4.8.For the marginally stable case, we solve the electron and ion heating equations numerically and find that rapid anomalous Ohmic heating occurs in a substantial plasma volume. This large hot plasma emits thermal bremsstrahlung hard X-rays ( 20 keV) comparable to, or exceeding, the nonthermal bremsstrahlung which would have been emitted by the beam in a conventional thick target, large area, collisional scenario without anomalous effects. This means that, contrary to the usual assumption, onset of return current instability need not turn off hard X-ray production by a beam, though changing its source from direct to indirect. Indeed with small beam areas, this indirect mechanism can result in a higher hard X-ray bremsstrahlung efficiency than in a conventional collisional thick target.The catastrophic heating regime, for which we expect much larger wave levels, is discussed qualitatively, and preliminary results cited of an alternative approach, incorporating an equation directly describing the electrostatic wave energy level. Which of these two regimes will pertain in any particular case depends (discontinuously) on the beam and atmospheric parameters and we suggest that this effect may manifest itself in the distinctive temporal behaviour of X-ray flares.  相似文献   

20.
Recently, it has been proposed that there exists a highly statistically significant (at 98% level of confidence) relationship between37Ar production rate (viz., solar neutrinos) and the Ap geomagnetic index (viz., solar particles), based on the X -square goodness-of-fit test and correlation analysis, for the interval 1970–1990. While a relationship between the two parameters, indeed, seems to be discernible, the strength of the relationship has been overstated. Instead of being significant at the afore-mentioned level of confidence, the relationship is found to be significant at only 95% level of confidence, based on Yates' modification to the X -square test for 2 × 2 contingency tables. Likewise, while correlation analysis yields a value ofr = 0.2691, it is important to note that such a value suggests that only about 7% of the variance can be explained by the inferred correlation and that the remaining 93% of the variance must be attributed to other sources.  相似文献   

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