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1.
We have obtained empirical relations between the p-mode frequency shift and the change in solar activity indices. The empirical relations are determined on the basis of frequencies obtained from BBSO and GONG stations during solar cycle 22. These relations are applied to estimate the change in mean frequency for the cycle 21 and 23. A remarkable agreement between the calculated and observed frequency shifts for the ascending phase of cycle 23, indicates that the derived relations are independent of epoch and do not change significantly from cycle to cycle. We propose that these relations could be used to estimate the shift in p-mode frequencies for past, present and future solar activity cycles, if the solar activity index is known. The maximum frequency shift for cycle 23 is estimated to be 265±90 nHz, corresponding to a predicted maximum smoothed sunspot number 118.1±35. 相似文献
2.
A detector sharing the orbital rate of Venus has a unique perspective on solar periodicities. Fourier analysis of the 8.6 year record of solar EUV output gathered by the Langmuir probe on Pioneer Venus Orbiter shows the influences of global oscillation modes located in the convective envelope and in the radiative interior. Seven of the eight lowest angular harmonic r-mode families are detected by their rotation rates which differ almost unmeasurably from ideal theoretical values. This determines a mean sidereal rotation rate for the envelope of 457.9 ± 2.0 nHz which corresponds to a period of 25.3 days. Many frequencies are aliased at ± 106 nHz by modulation from the lowest angular harmonic r-mode in the envelope. The rotation of this mode seems slightly retrograde, -1.5 ± 2.0 nHz, but small positive values are not excluded. We confirm that the rotation of the radiative interior, 381 nHz, is slower than the envelope by detecting g-mode frequencies for angular harmonics, 2 l 6, and a possible first detection of the rotation rate for the l = 1 case. Solar EUV lacks the sudden darkenings (dips) shown by visible irradiance; vortex cores in the photosphere and below are again suggested as a possible explanation. 相似文献
3.
R. H. Dicke 《Solar physics》1988,115(1):171-181
It has previously been shown that the statistics of the phase fluctuation of the sunspot cycle are compatible with the assumption that the solar magnetic field is generated deep in the Sun by a frequency stable oscillator and that the observed substantial phase fluctuation in the sunspot cycle is due to variation in the time required for the magnetic field to move to the solar surface (Dicke, 1978, 1979). It was shown that the observed phase shifts are strongly correlated with the amplitude of the solar cycle. It is shown here that of two empirical models for the transport of magnetic flux to the surface, the best fit to the data is obtained with a model for which the magnetic flux is carried to the surface by convection with the convection velocity proportional to a function of the solar cycle amplitude. The best fit of this model to the data is obtained for a 12-yr transit time. The period obtained for the solar cycle is T = 22.219 ± 0.032 yr. It is shown that the great solar anomaly of 1760–1800 is most likely real and not due to poor data. 相似文献
4.
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
5.
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
6.
We report on results from photographic observations of photospheric oscillations as a function of depth. Using rms-values and power-spectra from shifts of entire line-profiles, we find qualitatively an increase of the velocity-amplitude with increasing height. We get more quantitative informations by comparing measured asymmetries of line-profiles with calculated ones derived from Voigt-functions containing a depth dependent velocity-field.We find the scale-height H
0 of photospheric velocity oscillations to be 930±100 km. This result is to be compared with H
0 = 1100±200 km obtained by Canfield (1976), who used velocity weighting functions of the line centres.Further, we show that a general observed line asymmetry of medium strong lines (c-shape) does not depend on the phase of oscillations.Mitt. aus dem Kiepenheuer-Institut Nr. 178. 相似文献
7.
Robert M. Wilson 《Solar physics》1988,117(2):269-278
Because of the bimodal distribution of sunspot cycle periods, the Hale cycle (or double sunspot cycle) should show evidence of modulation between 20 and 24 yr, with the Hale cycle having an average length of about 22 yr. Indeed, such a modulation is observed. Comparison of consecutive pairs of cycles strongly suggests that even-numbered cycles are preferentially paired with odd-numbered following cycles. Systematic variations are hinted in both the Hale cycle period and R
sum (the sum of monthly mean sunspot numbers over consecutively paired sunspot cycles). The preferred even-odd cycle pairing suggests that cycles 22 and 23 form a new Hale cycle pair (Hale cycle 12), that cycle 23 will be larger than cycle 22 (in terms of R
M, the maximum smoothed sunspot number, and of the individual cycle value of R
sum), and that the length of Hale cycle 12 will be longer than 22 yr. Because of the strong correlation (r = 0.95) between individual sunspot cycle values of R
sum and R
M, having a good estimate of R
Mfor the present sunspot cycle (22) allows one to predict its R
sum, which further allows an estimation of both R
Mand R
sum for cycle 23 and an estimation of R
sum for Hale cycle 12. Based on Wilson's bivariate fit (r = 0.98), sunspot cycle 22 should have an R
Mequal to 144.4 ± 27.3 (at the 3- level), implying that its R
sum should be about 8600 ± 2200; such values imply that sunspot cycle 23 should have an R
sum of about 10500 ± 2000 and an R
Mof about 175 ± 40, and that Hale cycle 12 should have an R
sum of about 19100 ± 3000. 相似文献
8.
Using data from SOI-MDI (Haber et al., 2000), we compute the local frequencies of high-degree p modes and f modes. The frequencies are obtained through ring-diagram mode fitting. The Dense-Pack data set consists of a mosaic of 189 overlapping tiles, each tracked separately at the surface rotation rate over 1664-min time intervals during the Dynamics Programs. Each tile is 16° square and the tile centers are separated by 7.5° in latitude and longitude. For each sampling day and for each tile, we have computed the frequency shift measured relative to the temporal and spatial average of the entire set of frequencies. The motion of active regions as they rotate across the solar disk is vividly traced by these measurements. Active regions appear as locations of large positive frequency shifts. If the shifts are averaged over the solar disk and are scaled down to the appropriate wave number regime, the magnitude and frequency dependence of the shifts are consistent with the measured changes in global oscillation frequencies that occur over the solar cycle. As with the frequency shifts of low-degree global oscillations, the frequency dependence of the shifts indicates that the physical phenomena inducing the shifts is confined to the surface layers of the Sun. 相似文献
9.
Mykola I. Pishkalo 《Solar physics》2006,233(2):277-290
We have investigated the correlation between the relative sunspot number and tilt of the heliospheric current sheet (HCS)
in solar cycles 21–23. Strong and highly significant positive correlation (r > 0.8, P < 0.001) was found for corresponding data in the time interval from May 1976 through December 2004. Cross-correlation analysis
does not reveal any time shift between the data sets. Reconstructed values of the HCS tilt, for the time interval before 1976,
are found using sunspot numbers. To take different amplitude of solar cycles into account they were then normalized to zero
in the minima of the solar activity and to average in solar cycles 21–23 maximal calculated HCS tilt in the maxima. These
normalized reconstructed HCS data are compared with the angular positions of the brightest coronal streamers observed during
total solar eclipses in 1870–2002, and their agreement is better for the minima of the solar activity than for the maxima. 相似文献
10.
During solar cycle 23, 82 interplanetary magnetic clouds (MCs) were identified by the Magnetic Field Investigation (MFI) team
using Wind (1995 – 2003) solar wind plasma and magnetic field data from solar minimum through the maximum of cycle 23. The average occurrence
rate is 9.5 MCs per year for the overall period. It is found that some of the anomalies in the frequency of occurrence were
during the early part of solar cycle 23: (i) only four MCs were observed in 1999, and (ii) an unusually large number of MCs
(17 events) were observed in 1997, just after solar minimum. We also discuss the relationship between MCs, coronal mass ejections
(CMEs), and geomagnetic storms. During the period 1996 – 2003, almost 8000 CMEs were observed by SOHO-LASCO. The occurrence
frequency of MCs appears to be related neither to the occurrence of CMEs as observed by SOHO LASCO nor to the sunspot number.
When we included “magnetic cloud-like structures” (MCLs, defined by Lepping, Wu, and Berdichevsky, 2005), we found that the
occurrence of the joint set (MCs + MCLs) is correlated with both sunspot number and the occurrence rate of CMEs. The average
duration of the MCL structures is ~40% shorter than that of the MCs. The MCs are typically more geoeffective than the MCLs,
because the average southward field component is generally stronger and longer lasting in MCs than in MCLs. In addition, most
severe storms caused by MCs/MCLs with Dst
min≤ −100 nT occurred in the active solar period. 相似文献
11.
Smoothed monthly mean Ap indices are decomposed into two components (Ap)
c and (Ap)
n. The former is directly correlated with the current sunspot numbers, while the latter is shown to achieve its maximum correlation with the sunspot numbers after some time lag. This latter property is used to develop a method for predicting the sunspot maximum based on the observed value of (Ap)
n maximum which occurs during the preceding cycle. The value of R
M for cycle 23 predicted by this method is 149.3 ± 19.9. A method to estimate the rise time (from solar minimum to maximum) has been developed (based on analyses of Hathaway, Wilson, and Reichmann, 1994) and yields a value of 4.2 years. Using an estimate that the minimum between cycles 22 and 23 occurred in May 1996, it is predicted that the sunspot maximum for cycle 23 will occur in July 2000. 相似文献
12.
S. C. Tripathy Brajesh Kumar Kiran Jain A. Bhatnagar 《Journal of Astrophysics and Astronomy》2000,21(3-4):357-360
Using intermediate degreep-mode frequency data sets for solar cycle 22, we find that the frequency shifts and magnetic activity indicators show a &#x201C;hysteresis&#x201D;
phenomenon. It is observed that the magnetic indices follow different paths for the ascending and descending phases of the
solar cycle while for radiative indices, the separation between the paths are well within the error limits. 相似文献
13.
We study the meridional flow of small magnetic features, using high-resolution magnetograms taken from 1978 to 1990 with the NSO Vacuum Telescope on Kitt Peak. Latitudinal motions are determined by a two-dimensional crosscorrelation analysis of 514 pairs of consecutive daily observations from which active regions are excluded. We find a meridional flow of the order of 10 m s–1, which is poleward in each hemisphere, increases in amplitude from 0 at the equator, reaches a maximum at mid-latitude, and slowly decreases poleward. The average observed meridional flow is fit adequately by an expansion of the formM () = 12.9(±0.6) sin(2) + 1.4(±0.6) sin(4), in m s–1 where is the latitude and which reaches a maximum of 13.2 m s–1 at 39°. We also find a solar-cycle dependence of the meridional flow. The flow remains poleward during the cycle, but the amplitude changes from smaller-than-average during cycle maximum to larger-than-average during cycle minimum for latitudes between about 15° and 45°. The difference in amplitude between the flows at cycle minimum and maximum depends on latitude and is about 25% of the grand average value. The change of the flow amplitude from cycle maximum to minimum occurs rapidly, in about one year, for the 15–45° latitude range. At the highest latitude range analyzed, centered at 52.5°, the flow is more poleward-than-average during minimumand maximum, and less at other times. These data show no equatorward migration of the meridional flow pattern during the solar cycle and no significant hemispheric asymmetry. Our results agree with the meridional flow and its temporal variation derived from Doppler data. They also agree on average with the meridional flow derived from the poleward migration of the weak large-scale magnetic field patterns but differ in the solar-cycle dependence. Our results, however, disagree with the meridional flow derived from sunspots or plages.Operated by the Association of Universities for Research in Astronomy, Inc. under cooperative agreement with the National Science Foundation. 相似文献
14.
Prediction of the sunspot maximum of solar cycle 23 by extrapolation of spectral components 总被引：3，自引：0，他引：3
A simple method MEM-MRA, where spectral peaks are located by MEM (Maximum Entropy Method) and about a dozen most prominent ones are used in MRA (Multiple Regression Analysis) to estimate their amplitudes and phases, was applied to the sunspot number (Rz) series of 1748–1996. Spectral characteristics were different in the successive 3 intervals of 83 years each. Hence, for predictions, only data for the recent 83 years were considered relevant. From the spectra for 1914–1996, the most significant peaks at 5.3, 8.3, 10.5, 12.2, 47 years were used for reconstruction. The match between observed and reconstructed values was good (correlation +0.90). When extrapolated, the reconstructed values indicate a sunspot number maximum for the present solar cycle 23 as 140±9, to occur in year 2000 and for the next solar cycle 24 as 105±9, to occur in year 2010–2011. 相似文献
15.
We calculated the Hurst exponent H for the daily averaged intensity Q of optical flares, an index which describes the solar activity. We found that H0.74±0.02 in the range of scales from about 20 days up to 450 days. This value is well beyond H=
, expected for a stochastic Brownian process, thus indicating that the solar cycle could show persistence on small scales, in agreement with what has been found using other indices of the solar cycle. 相似文献
16.
More than 20 real periodicities ranging from 20 days to 2 years modulate the solar irradiance data accumulated since November 1978 by Nimbus 7. Many are quite strong during the first three years (solar maximum) and weak after that. There is a high correspondence between periods in irradiance and 28 periods predicted from the rotation and beating of global solar oscillations (r-modes and g-modes). Angular states = 1, 2, and 3 are detected as well as some unresolved r-mode power at higher . The prominence of beat periods implies a nonlinear system whose effective nonlinear power was measured to be about 2. This analysis constitutes a detection of r-modes in the Sun and determines from them a mean sidereal rotation rate for the convective envelope of 459 ± 4 nHz which converts to a period of 25.2 days (27.ld, synodic). 相似文献
17.
Fast Fourier analysis of the detrended record of solar irradiance obtained by the Nimbus-7 cavity pyrheliometer shows a rich spectrum of significant frequencies between about 30 and 850 nHz (periods between 13 and 400 days). Wolff and Hickey (1987a, b), elaborating on a model developed by Wolff (1974a, b, 1976, 1983, 1984), suggest that many of these peaks arise due to interference of rigidly rotating global solar oscillations (r- and g-modes). Their model fit is quite good in the region above about 135 nHz, but less satisfactory below this threshold. We note that the FFT spectrum of d2
L/d2
t, the second derivative of angular momentum of the solar inertial motion, contains peaks matching the large peaks in the irradiance spectrum below 400 nHz with periods near 0.08, 0.24, 0.65, and about 1 yr. We discuss the origins of the peaks in the d2
L/d2t spectra and review some previous studies bearing on the question of a possible relationship of solar motion and solar activity. The future persistence of the observed spectral peaks of irradiance with periods near 0.24 and 0.65 yr will provide a key test for this hypothesis. 相似文献
18.
The 1974–1988 Crimean measurements of the solar line-of-sight velocity continue to show the presence of a statistically significant periodicity P
1 = 160.009 (±) min with an average harmonic amplitude of about 21 cm s–1. The period is supposed to be that of the global pulsation of the Sun but with a little-known physical mechanism of excitation.The new observations give some evidence for the existence of a second periodicity, P
1 = 160.014 (±) min. It is hypothesized that the appearance of P
1 might be a sidelobe mode (of the P
0-oscillation) induced by rapid rotation of the central solar core.It is also noted that the spacing, in frequency, between P
0 and P
1, corresponds to a beat period of 10 ± 3 yr, which happens to be in good agreement with the average duration of the 11 yr cycle of the magnetic activity of the Sun. Accordingly, we suppose that the phase shift of the P
0-mode between the 1974–1982 and 1986–1988 time intervals reflects a remarkable change of the general magnetic field of the Sun in the course of the 22 yr solar cycle. 相似文献
19.
We present the results of an analysis of the winds of two WC10 central stars of planetary nebulae, CPD-56°8032 and He 2-113. These two stars have remarkably similar spectra, although the former exhibits somewhat broader emission line widths. High resolution spectra (up to R=50 000) were obtained in May 1993 for both objects at the 3.9 m AAT, using the UCL Echelle Spectrograph. The fluxes in individual Cii auto-ionising multiplet components, many of which were blended, were derived. Lines originating from auto-ionising resonance states situated in the C2+ continuum are very sensitive to the electron temperature, since the population of the these levels is close to LTE. The measured widths and profile shapes of these transitions are presented and are in excellent agreement with those predicted on the basis of their calculated auto-ionising lifetimes. The wind electron temperature is derived for both stars from the ratio of the fluxes in four such transitions (T
e
=18 500 K±1 500 K for CPD-56° 8032 andT
e
=13 600 K±800 K for He 2-113). Optical depth effects are investigated using normal recombination lines to obtain an independent wind electron temperature estimate in excellent agreement with the dielectronic line analysis. 相似文献
20.
P. A. Sturrock 《Solar physics》2008,252(1):1-18
Time – frequency analysis of data from the GALLEX and GNO solar neutrino experiments shows that some features in power-spectrum
analyses of those datasets are due to aliasing (a result of the fact that run durations tend to be small multiples of one
week). Displays formed from the published GALLEX data show a sharp discontinuity that we attribute to some systematic effect.
We therefore normalize data for each of the four experiments in the GALLEX series and concatenate the resulting normalized
data. This step effectively removes the presumed systematic effect. To help understand the effect of aliasing, we form time – frequency
displays of the two principal modulations found in the data, at 11.87 year−1 and at 13.63 year−1. We also form time – frequency displays of datasets formed by subtracting these modulations from the actual (normalized)
data. The results suggest that the true principal modulation is that at 11.87 year−1. Comparison with helioseismology data suggests that modulation may be occurring in the core, perhaps resulting from inhomogeneities
and fluctuations in the nuclear-burning process, and that the sidereal rotation rate of the core is 12.87 year−1, or 408 nHz. 相似文献