Wavelet Analysis of Solar Activity

Using wavelet analysis approach, the temporal variations of solar activity on time scales ranging from days to decades, are examined from the daily time series of sunspot numbers. A hierarchy of changing complex periods are careful detected and related cycles compared with results from recent similar analyses. A general determination of the main Schwabe cycle length variations is also suggested on the basis of the wavelet amplitude distribution extracted from the local wavelet power map.Comment: Postscript v1.1, 11 pages with 3 color figure

Solar cycle activity: an early prediction for cycle #25

Solar activity forecasting is an important topic for numerous scientific and technological areas, such as space mission operations, electric power transmission lines, power transformation stations and earth geophysical and climatic impact. Nevertheless, the well-known difficulty is how to accurately predict, on the basis of various recorded solar activity indices, the complete evolution of future solar cycles, due to highly complex dynamical and stochastic processes involved, mainly related to interaction of different components of internal magnetic fields. There are two main distinct classes of solar cycle prediction methods: the precursor-like ones and the mathematical-numerical ones. The main characteristic of precursor techniques, both purely solar and geomagnetic, is their physical basis. Conversely, the non-precursor methods use different mathematical and/or numerical properties of the known temporal evolution of solar activity indices to extract useful information for predicting future activity. For current solar cycle #24 we obtained fairly good statistical performances from both precursor and purely numerical methods, such as the so-called solar precursor and nonlinear ones. To further check the performances of these prediction techniques, we compared the early predictions for the next solar cycle #25. Preliminary results support some coherence of the prediction methods considered and confirm the current trend of a relatively low solar activity.Comment: 6 pages, 1 figur

Detecting Nonlinearity in Pressure Data Inside the Draft Tube of a Real Francis Turbine

A general method for testing nonlinearity in time series is described and applied to measurements of different pressure data inside the draft tube surge of a real Francis turbine. Comparing the current original time series to an ensemble of surrogates time series, suitably constructed to mimic the linear properties of the original one, we was able to distinguish a linear stochastic from a nonlinear deterministic behaviour and, moreover, to quantify the degree of nonlinearity present in the related dynamics. The problem of detecting nonlinear structure in real data is quite complicated by the influence of various contaminations, like broadband noise and/or long coherence times. These difficulties have been overcame using the combination of a suitable nonlinear filtering technique and a qualitative redundancy statistic analysis. The above investigations allow a quantitative characterization of different dynamical regimes of motion of gas cavities inside real turbines and, moreover, allow to support the reliability of some related mathematical modelizations.Comment: uuencoded compressed postscript file, 12 pages paper with included figures. (source file: 4.9 Mb

Reconstructed Total Solar Irradiance as a precursor for long-term solar activity predictions: a nonlinear dynamics approach

Total solar irradiance variations, about 0.1% between solar activity maximum and minimum, are available from accurate satellite measurements since 1978 and thus do not provide useful information on longer-term secular trends. Recently, Krivova et al., 2007 reconstructed, using suitable models, the total solar irradiance from the end of the Maunder minimum to the present, based on variations of the surface distribution of the solar magnetic field. The latter is calculated from the long historical record of the sunspot numbers using a simple but consistent physical model. There are many classes of proposed prediction methods for solar cycles behavior, based on different direct solar activity indices or on various valuable proxies. In particular, the precursor based methods, utilize a given proxy index to predict the future evolution of solar activity. Long-term time series of sunspot numbers, allow us to reliably predict the behavior of the next solar cycle, few years in advance. In previous papers we predicted the full-shape curve of future solar cycles, using a proper non-linear dynamics method applied to monthly smoothed sunspot numbers. In particular, we proved that a sufficiently reliable phase-amplitude prediction of the current solar cycle 24, requires the knowledge of the initial increasing phase of the cycle spanning at least two years. The aim of the present paper is to give a robust long-term prediction of solar cycle activity, many years in advance and for at least three successive solar cycles using the same nonlinear method and, as solar activity proxy index, the reconstructed total solar irrandiance.Comment: 16 pages, 9 figure

Solar cycle full-shape predictions: a global error evaluation for cycle 24

There are many proposed prediction methods for solar cycles behavior. In a previous paper we updated the full-shape curve prediction of the current solar cycle 24 using a non-linear dynamics method and we compared the results with the predictions collected by the NOAA/SEC prediction panel, using observed data up to October 2010. The aim of the present paper is to give a quantitative evaluation, a posteriori, of the performances of these prediction methods using a specific global error, updated on a monthly basis, which is a measure of the global performance on the predicted shape (both amplitude and phase) of the solar cycle. We suggest also the use of a percent cycle similarity degree, to better evaluate the predicted shape of the solar cycle curve.Comment: 12 pages, 4 figure

On the better constraints from the South Pole Telescope Sunyaev-Zel'dovich galaxy clusters survey: a FoM evaluation for the equation of state of Dark Energy

In a recent article by Benson et al., 2011, the authors show the latest measurements from the South Pole Telescope (SPT) Sunyaev Zel'dovich (SZ) cluster survey to better constrain some cosmological parameters. In particular, the authors found that adding the SPT cluster data significantly improves the constraints on equation of state of dark energy, w, beyond those found when using measurements of the CMB, supernovae, BAO and the Hubble constant. The main aim of the present research note is to give a further quantitative estimation of the above better constraints, through the computation of the Figure of Merit (FoM) applied to \Omega_m and w plots for the 68% and 95% confidence regions. This allows a better evaluation and a better comparison of the continuous improvements on the cosmological constraints, obtained using new different cosmological probes and different surveys.Comment: 9 pages, 3 figure

On the Distinct Periodicities of Sunspot Counts in Flaring and Non-flaring Active Regions

In a recent work, Kilcik et al. (2017), have detected the temporal and periodic behavior of sunspot counts (SSC) in flaring (i.e. C, M, or X class flares), and non-flaring active regions for the last two solar cycles, covering the period: 1996 - 2016. The main results obtained are: 1) The temporal behavior of monthly means of daily total SSC in flaring and non-flaring active regions are different and these differences are also varying from cycle to cycle; 2) The periodicities detected in SSC of flaring and non-flaring active regions are quite different and these variations are also different from one cycle to another; the highest detected period in the flaring active regions is 113 days, while there are much higher periodicities (327, 312, and 256 days) in non-flaring regions. The detection of typical different periodicities in flaring and non-flaring regions can suggests both important differences and physical interpretation in the magneto-hydrodynamic behavior of the Sun. For this reason in the present paper we show a further periodicity analysis of the sunspot counts in flaring and in non-flaring active regions using the same data source of that used by the above cited authors and applying a powerful wavelet analysis tool which is particularly useful to detect multiscale features of complex unsteady and unevenly sampled time series. In order to futher support the differences and similarities found in the time behavior of SSC in flaring and non-flaring regions, we also computed the behavior of the wavelet entropy, a proper time function which allow us to measure the degree of complexity in the dynamics of the related time series.Comment: 11 pages, 3 figure

Wavelet entropy as a measure of solar cycle complexity

Using wavelet analysis approach, we can derive a measure of the disorder content of solar activity, following the temporal evolution of the so-called wavelet entropy. The interesting feature of this parameter is its ability to extract a dynamical complexity information, in terms of frequency distribution of the energy content, avoiding restrictions, common in the nonlinear dynamics theory, such as stationarity. The analysis is performed on the monthly time series of sunspot numbers. From the time behaviour of the wavelet entropy we found a clear increase in the disorder content of solar activity for the current 23th solar cycle. This result suggests general low accuracies for current solar cycleprediction methods. Moreover, we pointed out a possible connection between wavelet entropy behaviour and solar excursion phases of solar dipole.Comment: 4 pages with 3 figures. Accepted for publication in Astronomy and Astrophysics Journa

Wavelet analysis of solar magnetic strength indices

Wavelet analysis of different solar activity indices, sunspot numbers, sunspot areas, flare index, magnetic fields, etc., allows us to investigate the time evolution of some specific features of the solar activity and the underlying dynamo mechanism. The main aim of this work is the analysis of the time-frequency behavior of some magnetic strengtht indices currently taken at the Mt. Wilson Observatory 150-Foot Solar Tower. In particular, we analyzed both the long time series (Jan 19, 1970 - Jan 22, 2013) of the Magnetic Plage Strength Index (MPSI) values and of the Mt. Wilson Sunspot Index (MWSI) values, covering the descending phase of cycle 20, the full solar cycles 21-23 and the current part of the 24 solar cycle. This study is a further contribution to detect the changes in the multiscale quasiperiodic variations in the integrated magnetic solar activity with a comparison between past solar cycles and the current one, which is one of the weaker recorded in the past 100 years. Indeed, it is well known that an unusual and deep solar minimum occurred between solar cycles 23 and 24 and the time-frequency behavior of some magnetic strengtht indices can help to better interpret the responsible mechanisms.Comment: 8 pages, 2 figure

A general parametric model for the dynamic dark energy

In the present work we suggest new and more generalized parameterizations for the Equation of State, EoS, of dark energy, maintaining the basic structure of two-parameters CPL-model, but covering both the past and the future of the cosmic history, without divergences and consistently with the current observational data. We propose two generalizations, starting from the extended MZp-model by Ma and Zhang, 2011, the $\xi$MZp-model and the DFp-model. The potential advantages of using these new formulations is their extended range of validity, mainly in the future, to determine possible future scenarios of the cosmic evolution.Comment: 9 page