Daniel Jean Roger Nordemann

RECONSTRUCTION OF WOLF SUNSPOT NUMBERS ON THE BASIS OF SPECTRAL CHARACTERISTICS AND ESTIMATES OF ASSOCIATED RADIO FLUX AND SOLAR WIND PARAMETERS FOR THE LAST MILLENNIUM

A reconstruction of sunspot numbers for the last 1000 years was obtained using a sum of sine waves derived from spectral analysis of the time series of sunspot number Rz for the period 1700–1999. The time series was decomposed in frequency levels using the wavelet transform, and an iterative regression model (ARIST) was used to identify the amplitude and phase of the main periodicities. The 1000-year reconstructed sunspot number reproduces well the great maximums and minimums in solar activity, identified in cosmonuclides variation records, and, specifically, the epochs of the Oort, Wolf, Spörer, Maunder, and Dalton Minimums as well the Medieval and Modern Maximums. The average sunspot number activity in each anomalous period was used in linear equations to obtain estimates of the solar radio flux F10.7, solar wind velocity, and the southward component of the interplanetary magnetic field.

SOLAR VARIABILITY EFFECTS STUDIED BY TREE-RING DATA WAVELET ANALYSIS

Abstract The global change approach to study the Sun-Earth system gives a growing amount of evidences that climate dynamics is affected by a large number of factors. The solar variability is very likely to be among them. Natural records, such as tree ring data, can be investigated to study the past global and regional climate, which was influenced by the solar radiative output variations, associated to solar activity. Wavelet transform analysis was applied to sunspot number and tree ring width time series from 1837 to 1996 at Concordia, Brazil. The amplitude and cross-amplitude spectral representation in the time-frequency domain allowed us to detect the occurrence of predominant periodicities and the relationship between the sunspot number and the tree ring time series. The Morlet complex wavelet analysis was used to study the most important variability factors on time scales ranging from from 2 to 100 years, and their stability in time, which is shown in both time series studied. We also applied the cross-wavelet spectral analysis to evaluate time delay among different tree ring time series, and between tree ring and sunspot number time series.

Comparative study between four classical spectral analysis methods

This work presents a comparison between four classical spectral analyses: Fourier, multitaper, maximum entropy and iterative regression. Six 256-sample artificial series were generated by superposition of sine functions, long trends (of time scale greater than series length) and noise (generated by pseudo-random function). A spectral analysis of an observational time series (sunspot number) was also performed. Advantages and drawbacks of every method are described in this work.

WAVELET ANALYSIS OF SOLAR-ENSO IMPRINTS IN TREE RING DATA FROM SOUTHERN BRAZIL IN THE LAST CENTURY

In order to study the imprint of solar and ENSO signals on terrestrial archives, the wavelet spectrum analysis was applied to solar-geophysical indices and tree ring data. Time series of Sunspot Number (SSN), southern oscillation index (SOI) and tree-ring indices from Southern Brazil, for the period 1876–1991, were used in this work. The 11-year solar cycle was present during the whole period in tree ring data, being more intense during 1930–1980, in agreement with an earlier study that was performed for thesame region but a different time range (1836–1996). ENSO effects on treering data from Southern Brazil were studied by the first time in this work using wavelet analysis. Short-term variations, between 2–5 years, arealso present in tree ring data. This represents the signature of ENSO events and was also observed in the SOI, as expected. The cross-wavelet spectrum analysis shows that both solar and climatic factors are recorded in tree ring data.

Principal components and iterative regression analysis of geophysical series: Application to Sunspot number (1750-2004)

We present here an implementation of a least squares iterative regression method applied to the sine functions embedded in the principal components extracted from geophysical time series. This method seems to represent a useful improvement for the non-stationary time series periodicity quantitative analysis. The principal components determination followed by the least squares iterative regression method was implemented in an algorithm written in the Scilab (2006) language. The main result of the method is to obtain the set of sine functions embedded in the series analyzed in decreasing order of significance, from the most important ones, likely to represent the physical processes involved in the generation of the series, to the less important ones that represent noise components. Taking into account the need of a deeper knowledge of the Suns past history and its implication to global climate change, the method was applied to the Sunspot Number series (1750-2004). With the threshold and parameter values used here, the application of the method leads to a total of 441 explicit sine functions, among which 65 were considered as being significant and were used for a reconstruction that gave a normalized mean squared error of 0.146.

Natural and artificial radionuclides in soils from Paraná State, Brazil

Soil samples from Paraná State, Brazil, were collected in 1991 and compared with others collected at the same location in March 1977 and at the end of 1983. Pedological analyses were practiced on these samples and137Cs and232Th,226Ra and40K activities were determined by gammaray spectrometry. A latitude dependence of137Cs was found as well. It was impossible to determine the137Cs contribution from Chernobyl nuclear accident because of low fallout and intense leaching, erosion and re-suspension in soils of regions with high annual precipitation. Natural radionuclides did not show such effects.

Sunspot number, solar activity index

On ´ umero de manchas solares ´ondice mais antigo da atividade solar, com observac ¸˜ oes de manchas solares estendendo-se desde 1611. Ele serve como uma medida da atividade magnetica geral do Sol. Neste trabalho apresentamos uma descric ¸˜ ao das caracter´osticas f´ osicas das manchas solares, a definic ¸˜ ao do numero de manchas solares, uma analise espectral do mesmo e uma reconstruc ¸˜ ao de 1000 anos. The sunspot number is the longest solar activity index available with observations since 1611. It is a measure of the general state of solar magnetic activity. In this work we present a desciption of sunspot physical caracte- ristics, the definition of the sunspot number, a spectral analysis and a reconstruction for the last 1000 years of the sunspot number.

Correlation of natural and artificial radionuclides in soils with pedological, climatological and geographic parameters

Various types of soil samples were collected in the southern part of Brazil, with depth intervals of 5 cm, down to 50 cm, using a specially designed sampler. Pedological analysis of these soils were performed. Nuclear activities of137Cs (expressed in Bq m−2) and radioactive natural element (226Ra,228Ra and40K) concentrations were determined by low background gamma-ray spectrometry.137Cs concentrations were correlated with radioactive natural element concentrations and pedological, climatological and geographic parameters related to the soil samples collected.

Reconstruction and searching ozone data periodicities in southern Brazil (29ºS, 53ºW)

Ozone plays a very important role in the nature due its characteristics as a natural filter of ultraviolet solar radiation. Thus, it is pertinent for the scientific community to understand all natural influence factors involving ozone along with a large time series. In this work, a reconstruction of ozone time series obtained by Brewer spectrophotometer from 1994 to 2008 at the Southern Space Observatory (SSO) - 29oS, 53oW - Southern Brazil is presented. TOMS-OMI data were used to follow the days without data, where a coefficient of correlation between TOMS-OMI and Brewer is acceptable around r = 0.89. Besides, wavelet analysis to determine the temporal evolution of the frequencies and the amplitudes was applied. Moreover, wavelet analysis aiming to determine the temporal evolution of the frequencies and the amplitudes was performed. The results pointed a period of 365 days (1 yr) for the seasonal variation of ozone, of 600 days attributed for a possible QBO influence and two periods of 2000 and other 4000 days regarding possibly to the second harmonic of the 11-year solar cycle.

Long term relation between solar activity and surface temperature at different geographical regions

Global suface temperature has showed a rise trend in the last 150 years. This has been mainly attributed to the anthropogenic induced grenhouse gases emissions. However, the role of natural processes is not completely understood and should not be underestimated. In this work, we compare the long term variability of solar activity (as quantified by the sunspot number) with several surface temperature series from different geographical regions (global, hemispheric and latitudinal ranges). The interval of analysis is 1880-2005. The data are analyzed with wavelet multiresolution technique. It has been found that the solar activity long term trend has a maximum around 1970, while air surface temperature series showed maximum (still rising) at 2005. There are differences in the long term trend for Northern and Southern hemispheres. These differences and the relation with solar activity are discussed in this work.