Nivaor Rodolfo Rigozo

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.

A study of the latitudinal dependence of the quasi-biennial oscillation in Total Ozone Mapping Spectrometer total ozone

A wavelet multiresolution analysis of the quasi-biennial oscillation (QBO) latitudinal structure in total ozone is performed for the period 1979–1992 (Nimbus-7 TOMS data). It has been found that ozone is nearly in phase with the QBO signal in the equatorial region (0°—5° and 5°—10°), and it is out of phase (lag ~ +15 and —15 months in north and south) in the 10°—15° to 55°—60° latitudinal bands. The cross-correlation coefficient between total ozone and zonal wind index is high (>0.7) at latitudes lower than 10°, decreases in the transition region 10°—15° (r ~ 0.4) and it has a non-linear profile at high latitudes, with a maximum near the 25°—30° band. The correlation is observed to be higher in the Southern Hemisphere latitudinal bands. Spectral analysis was performed for each latitudinal range, and QBO period and amplitude profiles were obtained. A detailed latitudinal profile of the QBO signal in total ozone is obtained from the present analysis.

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.

South Tropical Atlantic anti-phase response to Holocene Bond Events

Records of the climatic impacts of the North Atlantic Bond cycles over the subtropical Southern Hemisphere re-main scarce, and their mechanism is a topic of active discussion. We present here an alkenone-based reconstruct-ed sea surface temperature (SST) of a sediment core retrieved from the Brazilian Southwestern Tropical Atlantic (SWTA), Rio de Janeiro, together with a sediment SST record from the Cariaco Basin. The sediment cores span the period 2,100 B.P. – 11,100 B.P. Morlet-wavelet analysis detected marked periodic signals of ~ 0.8, ~ 1.7 and ~2.2 kyr, very similar and with comparable phases to the hematite-stained-grain time series from the Northern North Atlantic in which the cyclic pattern was recognized as Bond cycles. Our result corroborates the modeled surface ocean anti-phase thermal relation between the North and the South Atlantic. We attribute this behavior to the slowing of the Atlantic Meridional Overturning Circulation. The relative SST warming at Rio de Janeiro and the relative cooling at Cariaco were comparatively more pronounced during the early Holocene (from 11 to 5 kyr B.P.) than in more recent time.

CORONAL MASS EJECTION DYNAMICS REGARDING RADIAL AND EXPANSION SPEEDS

A new technique for the detection of coronal mass ejection (CME) speeds using image processing was applied. This technique permits us to determine the CME dynamics: radial and expansion distances, velocities, and accelerations. The CME dynamics is determined by the selection of a radial direction in a given Large Angle and Spectroscopic Coronagraph image, which starts just before the occulter (close to the center) and extends to the extremity of the image. By taking a series of images and extracting the same radial direction, it is possible to have a time history of any moving feature along this direction. This technique allows us to choose the number of directions that is used in the CME detection to determine its dynamics. This paper presents the results for the dynamical features (radial and expansion) of five CME events observed on 1999 February 5, 2001 February 2, 2002 March 1, 2003 December 2, and 2007 December 31.

Preliminary design of the INPE's Solar Vector Magnetograph

We describe the preliminary design of a magnetograph and visible-light imager instrument to study the solar dynamo processes through observations of the solar surface magnetic field distribution. The instrument will provide measurements of the vector magnetic field and of the line-of-sight velocity in the solar photosphere. As the magnetic field anchored at the solar surface produces most of the structures and energetic events in the upper solar atmosphere and significantly influences the heliosphere, the development of this instrument plays an important role in reaching the scientific goals of The Atmospheric and Space Science Coordination (CEA) at the Brazilian National Institute for Space Research (INPE). In particular, the CEAs space weather program will benefit most from the development of this technology. We expect that this project will be the starting point to establish a strong research program on Solar Physics in Brazil. Our main aim is acquiring progressively the know-how to build state-of-art solar vector magnetograph and visible-light imagers for space-based platforms to contribute to the efforts of the solar-terrestrial physics community to address the main unanswered questions on how our nearby Star works.