Power spectrum analysis of BNL decay rate data

Abstract

Evidence for an anomalous annual periodicity in certain nuclear decay data has led to speculation concerning a possible solar influence on nuclear processes. As a test of this hypothesis, we here search for evidence in decay data that might be indicative of a process involving solar rotation, focusing on data for 32 Si and 36 Cl decay rates acquired at the Brookhaven National Laboratory. Examination of the power spectrum over a range of frequencies (10 -15 year -1 ) appropriate for solar synodic rotation rates reveals several periodicities, the most prominent being one at 11.18 year -1 with power 20.76. We evaluate the significance of this peak in terms of the false-alarm probability, by means of the shuffle test, and also by means of a new test (the "shake" test) that involves small random time displacements. The last two tests are the more robust, and indicate that the peak at 11.18 year -1 would arise by chance only once out of about 10 7 trials. However, the fact that there are several peaks in the rotational search band suggests that modulation of the count rate involves several low-Q oscillations rather than a single high-Q oscillation, possibly indicative of a partly stochastic process. To pursue this possibility, we investigate the running mean of the power spectrum, and identify a major peak at 11.93 year -1 with peak running-mean power 4.08. Application of the shuffle test indicates that there is less than one chance in 10 11 of finding by chance a value as large as 4.08.Application of the shake test leads to a more restrictive result that there is less than one chance in 10 15 of finding by chance a value as large as 4.08. We find that there is notable agreement in the running-mean power spectra in the rotational search band formed from BNL data and from ACRIM total solar irradiance data. Since rotation rate estimates derived from irradiance data have been found to be closely related to rotation rate estimates derived from low-energy solar-neutrino data, this result supports the recent conjecture that solar neutrinos may be responsible for variations in nuclear decay rates.We also carry out a similar comparison with local temperature measurements, but find no similarity between power spectra formed from BNL measurements and from local temperature measurements.3/31

Concerning the time dependence of the decay rate of 137Cs

“…community (Emery, 1972;Hahn et al, 1976;Dostal et al, 1977), and the results presented in ), Javorsek et al (2010, and Sturrock et al (2010aSturrock et al ( , 2010b, as well as others, have generated renewed interest in this topic. In an effort to further explore the possible existence of periodicities in nuclear decays, an examination of historical data collected during extended studies of half-lives of long-lived radionuclides and of detector stability has been carried out at the Physikalisch-Technische Bundesanstalt (PTB).…”

Solar influence on nuclear decay rates: constraints from the MESSENGER mission

“…In addition to annual periodicities, evidence for other periodicities in decay data possibly associated with solar rotation is reported in Sturrock et al (2010a), Sturrock et al (2010b), Fischbach et al (2011), andSturrock et al (2011), including evidence for a period of ∼33 days, and for a 2.11 yr −1 Rieger-like periodicity. Since none of the rotationrelated periodic signals (in what should be randomly distributed data) corresponds to any known terrestrial influence, these results support the inference of a solar origin to time-varying nuclear decay rates, through some as yet unknown mechanism .…”

“…In a recent series of papers Fischbach et al 2009;Sturrock et al 2010a;Javorsek II et al 2010;Sturrock et al 2010b) evidence has been presented for a possible solar influence on nuclear decay rates. Data analyzed by and Fischbach et al (2009) indicate a possible correlation between the solar flare of 13 December 2006 and a decrease in the measured decay rate of 54 Mn coincident in time with the flare.…”

Fast Calculation of the Lomb-Scargle Periodogram Using Graphics Processing Units

“…At the time of writing, NASA's Astrophysics Data System (ADS) lists 735 and 1,810 publications (respectively) that cite these two papers, highlighting how important the L-S periodogram has proven for the analysis of time series. Recent applications include the search for a link between solar rotation and nuclear decay rates (Sturrock et al 2010); the study of pulsar timing noise (Lyne et al 2010); the characterization of quasi-periodic oscillations in blazars (Rani et al 2010); and the measurement of rotation periods in exoplanet host stars (Simpson et al 2010).…”