48 research outputs found
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 yr-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 sidereal
frequency 12.85 yr-1. We find, by Monte Carlo calculations, 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 yr-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.Comment: 22 pages, 9 tables, 10 figure
Further Evidence Suggestive of a Solar Influence on Nuclear Decay Rates
Recent analyses of nuclear decay data show evidence of variations suggestive
of a solar influence. Analyses of datasets acquired at the Brookhaven National
Laboratory (BNL) and at the Physikalisch-Technische Bundesanstalt (PTB) both
show evidence of an annual periodicity and of periodicities with sidereal
frequencies in the neighborhood of 12.25 year^{-1} (at a significance level
that we have estimated to be 10^{-17}). It is notable that this implied
rotation rate is lower than that attributed to the solar radiative zone,
suggestive of a slowly rotating solar core. This leads us to hypothesize that
there may be an "inner tachocline" separating the core from the radiative zone,
analogous to the "outer tachocline" that separates the radiative zone from the
convection zone. The Rieger periodicity (which has a period of about 154 days,
corresponding to a frequency of 2.37 year^{-1}) may be attributed to an r-mode
oscillation with spherical-harmonic indices l=3, m=1, located in the outer
tachocline. This suggests that we may test the hypothesis of a solar influence
on nuclear decay rates by searching BNL and PTB data for evidence of a
"Rieger-like" r-mode oscillation, with l=3, m=1, in the inner tachocline. The
appropriate search band for such an oscillation is estimated to be 2.00-2.28
year^{-1}. We find, in both datasets, strong evidence of a periodicity at 2.11
year^{-1}. We estimate that the probability of obtaining these results by
chance is 10^{-12}.Comment: 12 pages, 6 figures, v2 has a color corrected Fig 6, a corrected
reference, and a corrected typ
Power Spectrum Analysis of Physikalisch-Technische Bundesanstalt Decay-Rate Data: Evidence for Solar Rotational Modulation
Evidence for an anomalous annual periodicity in certain nuclear decay data
has led to speculation concerning a possible solar influence on nuclear
processes. We have recently analyzed data concerning the decay rates of Cl-36
and Si-32, acquired at the Brookhaven National Laboratory (BNL), to search for
evidence that might be indicative of a process involving solar rotation.
Smoothing of the power spectrum by weighted-running-mean analysis leads to a
significant peak at frequency 11.18/yr, which is lower than the equatorial
synodic rotation rates of the convection and radiative zones. This article
concerns measurements of the decay rates of Ra-226 acquired at the
Physikalisch-Technische Bundesanstalt (PTB) in Germany. We find that a similar
(but not identical) analysis yields a significant peak in the PTB dataset at
frequency 11.21/yr, and a peak in the BNL dataset at 11.25/yr. The change in
the BNL result is not significant since the uncertainties in the BNL and PTB
analyses are estimated to be 0.13/yr and 0.07/yr, respectively. Combining the
two running means by forming the joint power statistic leads to a highly
significant peak at frequency 11.23/yr. We comment briefly on the possible
implications of these results for solar physics and for particle physics.Comment: 15 pages, 13 figure
Solar cycle variations in the growth and decay of sunspot groups
We analysed the combined Greenwich (1874-1976) and Solar Optical
Observatories Network (1977-2011) data on sunspot groups. The daily rate of
change of the area of a spot group is computed using the differences between
the epochs of the spot group observation on any two consecutive days during its
life-time and between the corrected whole spot areas of the spot group at these
epochs. Positive/negative value of the daily rate of change of the area of a
spot group represents the growth/decay rate of the spot group. We found that
the total amounts of growth and decay of spot groups whose life times > or = 2
days in a given time interval (say one-year) well correlate to the amount of
activity in the same interval. We have also found that there exists a
reasonably good correlation and an approximate linear relationship between the
logarithmic values of the decay rate and area of the spot group at the first
day of the corresponding consecutive days, largely suggesting that a
large/small area (magnetic flux) decreases in a faster/slower rate. There
exists a long-term variation (about 90-year) in the slope of the linear
relationship. The solar cycle variation in the decay of spot groups may have a
strong relationship with the corresponding variations in solar energetic
phenomena such as solar flare activity. The decay of spot groups may also
substantially contribute to the coherence relationship between the total solar
irradiance and the solar activity variations.Comment: 12 pages, 7 figures, Accepted for publication in Astrophysics & Space
Science. arXiv admin note: substantial text overlap with arXiv:1105.106
Coronal Magnetic Field Evolution from 1996 to 2012: Continuous Non-potential Simulations
Coupled flux transport and magneto-frictional simulations are extended to simulate the continuous magnetic-field evolution in the global solar corona for over 15 years, from the start of Solar Cycle 23 in 1996. By simplifying the dynamics, our model follows the build-up and transport of electric currents and free magnetic energy in the corona, offering an insight into the magnetic structure and topology that extrapolation-based models cannot. To enable these extended simulations, we have implemented a more efficient numerical grid, and have carefully calibrated the surface flux-transport model to reproduce the observed large-scale photospheric radial magnetic field, using emerging active regions determined from observed line-of-sight magnetograms. This calibration is described in some detail. In agreement with previous authors, we find that the standard flux-transport model is insufficient to simultaneously reproduce the observed polar fields and butterfly diagram during Cycle 23, and that additional effects must be added. For the best-fit model, we use automated techniques to detect the latitude–time profile of flux ropes and their ejections over the full solar cycle. Overall, flux ropes are more prevalent outside of active latitudes but those at active latitudes are more frequently ejected. Future possibilities for space-weather prediction with this approach are briefly assessed