On the fourier spectrum analysis of the solar neutrino capture rate

Periodic variations in Davis' experimental data concerning the solar neutrino capture rate are derived on the basis of a Fourier spectrum analysis. Variations in the ³⁷Ar production rate are obtained for a series of randomly spaced observations in the period 1970–1985 (runs 18–89). The harmonic analysis of runs 18–89 has determined solar neutrino capture rate variations with periods of 8.33, 5.00, 2.13, 1.61, 0.83, 0.61, 0.54, and 0.51 yr, thereby confirming earlier calculations performed for the set of runs 18–69 (1983), 18–74 (1985a), and 18–80 (1985b). The results also confirm those of Sakurai (1979) who showed that there is strong evidence that the observed solar neutrino flux has a tendency to vary with quasi-biennial periodicity. We show that the results of the Fourier spectrum analysis do not depend upon certain high or low values in Davis' experimental data.     

On the long-period variations and magnitude of the solar neutrino flux

We analyze the solar neutrino flux fluctuations using data from the Homestake, GALLEX, GNO, SAGE, and Super Kamiokande experiments. Spectral analysis and direct quantitative estimations show that the quasi-five-year periodicity is the most stable neutrino flux variation. Revised mean solar neutrino fluxes are presented. These are used to estimate the observed pp flux of the solar electron neutrinos near the Earth. We consider two alternative explanations for the origin of the variable component of the solar neutrino deficit.     

Multiple cycles of magnetic activity in the Sun and Sun-like stars and their evolution

The wavelet transform method for high-quality time-frequency analysis is applied to sets of observations of relative sunspot numbers and stellar chromosphere fluxes of 10 Sun-like stars.Wavelet analysis of solar data shows that in a certain interval of time there are several cycles of activity with periods of duration which vary considerably from each other:from quasi-biennial cycles to 100-yr cycles.Cyclic activity was detected in almost all Sun-like stars that we examined,even those that previously were not considered as stars with cyclic activity according to analysis using a Scargle periodogram.The durations of solar and stellar cycles significantly change during the observation period.     

Investigation of Quasi-periodic Solar Oscillations in Sunspots Based on SOHO/MDI Magnetograms

In this work we study quasi-periodic solar oscillations in sunspots, based on the variation of the amplitude of the magnetic field strength and the variation of the sunspot area. We investigate long-period oscillations between three minutes and ten hours. The magnetic field synoptic maps were obtained from the SOHO/MDI. Wavelet (Morlet), global wavelet spectrum (GWS) and fast Fourier transform (FFT) methods are used in the periodicity analysis at the 95?% significance level. Additionally, the quiet Sun area (QSA) signal and an instrumental effect are discussed. We find several oscillation periods in the sunspots above the 95?% significance level: 3??C?5, 10??C?23, 220??C?240, 340 and 470 minutes, and we also find common oscillation periods (10??C?23 minutes) between the sunspot area variation and that of the magnetic field strength. We discuss possible mechanisms for the obtained results, based on the existing models for sunspot oscillations.     

Time variations of the solar neutrino flux

The Fourier analysis of the argon-37 production rate for runs 18–80 observed in Davis's well-known solar neutrino experiment is presented. The method of Fourier analysis with the unequally-spaced data of Davis and associates is described and the discovered periods are compared with recently published results for the analysis of the data of runs 18–69. The harmonic analysis of the data of runs 18–80 shows time variations of the solar neutrino flux with periods =8.33, 5.26, 2.13, 1.56, 0.83, 0.64, 0.54, and 0.50 yr, respectively, which confirms earlier computations.     

The statistical study of quasi‐periodic oscillations of the radio emission in solar quiet regions

In this study we discuss variations of the radio emission from the Quiet Sun Areas (QSA) at centimeter wavelength (1.76 cm). Data were obtained from Nobeyama Radioheliograph (NoRH). Oscillations of selected areas were studied carefully from data taken over one week. We try to find quasi‐periodic solar oscillations from the QSA. We used the traditional Fast Fourier Transform (FFT), Global Wavelet Spectrum (GWS) and Wavelet (Morlet) for studying signals in the frequency/time‐frequency domain. We used the Fisher randomization test to verify the significance of the observed signal. Instrumental and sky noises were studied using a cross‐correlation analysis. Additionally, a single pixel analysis were done. Wide ranges of solar oscillation periods were found from the Quiet Sun Area (QSA): 3–15, 35–70, and 90 minutes. Some physical explanations are suggested for these oscillations. However, it is not possible to give a conclusive statement about the origin of the long quasi‐periodic (>60 min) oscillations from the QSA (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Relative phase analyses of long-term hemispheric solar flare activity

Wavelet transform methods, including the continuous wavelet transform, cross-wavelet transform and wavelet coherence, have been proposed to investigate the phase synchrony of the monthly mean flare indices in the time interval 1966 January–2007 December in the solar northern and southern hemispheres, respectively. The Schwabe cycle is the only period of statistical significance, and its mean value is 10.7 yr for the monthly mean flare indices in the northern hemisphere but slightly smaller, 10.1 yr, in the southern hemisphere – this should lead to phase asynchrony between the two. Both the cross-wavelet transform and wavelet coherence analyses show asynchronous behaviour with strong phase mixing in the high-frequency components of hemispheric flare activity, and strong synchronous behaviour with coherent phase angles in the low-frequency components, corresponding to the period-scales around the Schwabe cycle. The northern flare activity should lead the southern for the low-frequency components.     

On the homestake neutrino data

³⁷ Ar production rates from the Homestake experiment suggest a possible anticorrelation between solar neutrino flux and solar activity. In this paper we present results from linear correlation analyses between Homestake data and several solar activity parameters in the period 1970–1990. Our results support the hypothesis that Homestake neutrino fluxes exhibit a (positive or negative) correlation with those parameters, but they also suggest that the heliomagnetic field in the subphotosphere could be responsible for the observed flux modulation.     

Quasi-periodic variation in the solar neutrino flux revisited

Neutrino capture rate data from the Homestake chlorine experiment (1970–1990) has been spectrally analysed. The data were smoothed by a 4-month equally-spaced sequence and by a cubic spline polynomial approximation. Fourier (FFT), maximum entropy spectrum analysis (MESA), and power spectrum analysis (PSA) employing the Blackman-Tukey window were used. The significant periodicities obtained are: 1 ± 0.1, 1.4 ± 0.2, 2.4 ± 0.2, 5 ± 0.2, and 11 ± 1.5 years. A possible correlation with similar coincident periods in other solar-terrestrial phenomena is discussed.     

Activity cycle of solar filaments

Long-term variation in the distribution of the solar filaments observed at the Observatorie de Paris, Section de Meudon from March 1919 to December 1989 is presented to compare with sunspot cycle and to study the periodicity in the filament activity, namely the periods of the coronal activity with the Morlet wavelet used. It is inferred that the activity cycle of solar filaments should have the same cycle length as sunspot cycle, but the cycle behavior of solar filaments is globally similar in profile with, but different in detail from, that of sunspot cycles. The amplitude of solar magnetic activity should not keep in phase with the complexity of solar magnetic activity. The possible periods in the filament activity are about 10.44 and 19.20 years. The wavelet local power spectrum of the period 10.44 years is statistically significant during the whole consideration time. The wavelet local power spectrum of the period 19.20 years is under the 95% confidence spectrum during the whole consideration time, but over the mean red-noise spectrum of α = 0.72 before approximate Carrington rotation number 1500, and after that the filament activity does not statistically show the period. Wavelet reconstruction indicates that the early data of the filament archive (in and before cycle 16) are more noiseful than the later (in and after cycle 17).     

Combined Analysis of Solar Neutrino and Solar Irradiance Data: Further Evidence for Variability of the Solar Neutrino Flux and Its Implications Concerning the Solar Core

A search for any particular feature in any single solar neutrino dataset is unlikely to establish variability of the solar neutrino flux since the count rates are very low. It helps to combine datasets, and in this article we examine data from both the Homestake and GALLEX experiments. These show evidence of modulation with a frequency of 11.85 year⁻¹, which could be indicative of rotational modulation originating in the solar core. We find that precisely the same frequency is prominent in power spectrum analyses of the ACRIM irradiance data for both the Homestake and GALLEX time intervals. These results suggest that the solar core is inhomogeneous and rotates with a sidereal frequency of 12.85 year⁻¹. From Monte Carlo calculations, it is found that the probability that the neutrino data would by chance match the irradiance data in this way is only 2 parts in 10 000. This rotation rate is significantly lower than that of the inner radiative zone (13.97 year⁻¹) as recently inferred from analysis of Super-Kamiokande data, suggesting that there may be a second, inner tachocline separating the core from the radiative zone. This opens up the possibility that there may be an inner dynamo that could produce a strong internal magnetic field and a second solar cycle.     

大气臭氧周期变化的小波分析

根据小波分析的基本原理,应用Mexicohat子波作为小波基函数,对1979～1992年间大气臭氧含量的变化进行了逐日分析。结果表明：大阳活动与大气臭氧的变化有关。臭氧变化中的周期与太阳活动的周期变化极其类似。研究的结果与人们论述同一问题的文献结果相当吻合。     

The influence of solar system oscillation on the variability of the total solar irradiance

Total solar irradiance (TSI) is the primary quantity of energy that is provided to the Earth. The properties of the TSI variability are critical for understanding the cause of the irradiation variability and its expected influence on climate variations. A deterministic property of TSI variability can provide information about future irradiation variability and expected long-term climate variation, whereas a non-deterministic variability can only explain the past.This study of solar variability is based on an analysis of two TSI data series, one since 1700 A.D. and one since 1000 A.D.; a sunspot data series since 1610 A.D.; and a solar orbit data series from 1000 A.D. The study is based on a wavelet spectrum analysis. First, the TSI data series are transformed into a wavelet spectrum. Then, the wavelet spectrum is transformed into an autocorrelation spectrum to identify stationary, subharmonic and coincidence periods in the TSI variability.The results indicate that the TSI and sunspot data series have periodic cycles that are correlated with the oscillations of the solar position relative to the barycenter of the solar system, which is controlled by gravity force variations from the large planets Jupiter, Saturn, Uranus and Neptune. A possible explanation for solar activity variations is forced oscillations between the large planets and the solar dynamo.We find that a stationary component of the solar variability is controlled by the 12-year Jupiter period and the 84-year Uranus period with subharmonics. For TSI and sunspot variations, we find stationary periods related to the 84-year Uranus period. Deterministic models based on the stationary periods confirm the results through a close relation to known long solar minima since 1000 A.D. and suggest a modern maximum period from 1940 to 2015. The model computes a new Dalton-type sunspot minimum from approximately 2025 to 2050 and a new Dalton-type period TSI minimum from approximately 2040 to 2065.     

Short period variation of the photospheric magnetic field

The photospheric magnetic data recorded from August 12, 1959 to September 29, 1967 and averaged over Bartels rotation periods are treated as zonal terms of the solar magnetic field which is expanded in a series of spherical harmonics. Numerical analysis of the reduced data gives seven periods. Three of these seem to be essential in the superposed variation of the solar magnetic field. The first of them (17.74 yr) is thought to be a contribution from the magnetic cycle for the determination of which the data covering only 8 yr interval are of insufficient accurity. For this reason, a 22.2 yr period is favoured by the computations. The numerical values of the two shorter periods are deduced as 2.557 yr and 4.194 yr. The amplitudes and phase angles of the periodic terms in question are determined.     

Nature of Quiet Sun Oscillations Using Data from the Hinode, TRACE, and SOHO Spacecraft

We study the nature of quiet-Sun oscillations using multi-wavelength observations from TRACE, Hinode, and SOHO. The aim is to investigate the existence of propagating waves in the solar chromosphere and the transition region by analyzing the statistical distribution of power in different locations, e.g. in bright magnetic (network), bright non-magnetic and dark non-magnetic (inter-network) regions, separately. We use Fourier power and phase-difference techniques combined with a wavelet analysis. Two-dimensional Fourier power maps were constructed in the period bands 2??C?4?minutes, 4??C?6?minutes, 6??C?15?minutes, and beyond 15?minutes. We detect the presence of long-period oscillations with periods between?15 and 30?minutes in bright magnetic regions. These oscillations were detected from the chromosphere to the transition region. The Fourier power maps show that short-period powers are mainly concentrated in dark regions whereas long-period powers are concentrated in bright magnetic regions. This is the first report of long-period waves in quiet-Sun network regions. We suggest that the observed propagating oscillations are due to magnetoacoustic waves, which can be important for the heating of the solar atmosphere.     

太阳与地磁活动的1.3–1.7 yr振荡关系分析

太阳和地磁活动中的1.3–1.7 yr周期研究对于理解日地空间耦合系统中可能发生的物理过程十分重要.黑子是太阳光球层上最突出的磁场结构, Ap指数则是表征全球地磁活动水平的重要指标.使用同步压缩小波变换得到太阳黑子数和地磁Ap指数的1.3–1.7yr周期,并用互相关方法分析研究它们之间的相位关系.结果如下:(1)太阳黑子数和地磁Ap指数的1.3–1.7 yr周期呈现间歇性的演化特征,且随着时间的变化而不断变化;(2)地磁Ap指数在奇数活动周比相邻的偶数活动周的周期分量更高,表现出上下波动的变化特性;(3)地磁Ap指数和太阳黑子数的相位关系不是一成不变的,在大多数情况下地磁Ap指数滞后太阳黑子数,仅在第18和第22活动周黑子数在相位上滞后.     

The search for possible time variations in Davis' measurements of the argon production rate in the solar neutrino experiment

With the gradual accumulation of experimental data in the solar neutrino experiment of DAVIS and collaborators (runs 18–74 for 1970–1982), the question, whether there are time variations of the solar neutrino flux, is of renewed interest. We discuss the mathematical-numerical methods applied to the statistical analysis of DAVIS ' argon-37 production rate up till now known in the literature. These methods are characterized by the arbitrary arrangement of the DAVIS data in a time series. We perform a certain Fourier transformation for unequally-spaced time series of the measuring data of the argon-37 production rate, discuss the discovered periods and give significance criteria with respect to each period. We find that all periods discussed in the literature are contained in our series of periods. Pointing out the more mathematical character of the time series analysis we emphasize the predominant significance of the detected periods.     

Sun's inertial motion and luminosity

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.     

Long-Period Oscillations in Polar Plumes as Observed by cds on Soho

We examine spectral time series of the transition region line Ov 629Å, observed with the Coronal Diagnostic Spectrometer (CDS) on the SOHO spacecraft in July 1997. Both Fourier and wavelet transforms have been applied independently to the analysis of plume oscillations in order to find the most reliable periods. The wavelet analysis allows us to derive the duration as well as the periods of the oscillations. Our observations indicate the presence of compressional waves with periods of 10–25 min. We have also detected a 11±1 min periodicity in the network regions of the north polar coronal hole. The waves are produced in short bursts with coherence times of about 30 min. We interpret these oscillations as outward propagating slow magneto-acoustic waves, which may contribute significantly to the heating of the lower corona by compressive dissipation and which may also provide enough energy flux for the acceleration of the fast solar wind. The data support the idea that the same driver is responsible for the network and plume oscillations with the network providing the magnetic channel through which the waves propagate upwards from the lower atmosphere to the plumes.     

Processing Method Effects on Solar Diameter Measurements: Use of Data Gathered by the Solar Disk Sextant

To determine the apparent diameter of the Sun, it is first necessary to measure the shape of the intensity profile of the solar limb with an imaging optical system (hereafter denoted as a solar-limb profile). The inflection point of the limb profile is usually used as a reference for calculating the diameter. Because this point may be difficult to determine in the presence of noise, it is necessary to define an appropriate filtering process that eliminates noise while preserving the position of the inflection point. In this paper we study two filtering techniques, one based on the compact wavelet transform and the other on the finite Fourier transform definition, that meet these requirements. The application of these two techniques to data gathered by the Solar Disk Sextant experiment shows that the solar radius increased from 1992 to 1996 by about 197 mas. However, a previous analysis of the same data and our present analysis provide a difference in the measured radii of about 92 mas. We show that this difference is entirely traced to the filtering process.