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Interplanetary shock parameters are analyzed for solar maximum (year 2000) and solar minimum (years 1995-1996) activity. Fast forward shocks are the most usual type of shock observed in the interplanetary medium near Earth's orbit, and they are 88% of the identified shocks in 2000 and 60% in 1995-1996. Average plasma and magnetic field parameters for upstream and downstream sides of the shocks were calculated, and the parameter variations through the shock were determined. Applications of the Rankine-Hugoniot equations were made, obtaining shock speeds and Alfvenic Mach number. Static and dynamic pressures variations through the shocks were also calculated. Every parameter have larger variation through the shock in solar maximum than in solar minimum, with exception of the proton density. The intensity of shocks relative to the interplanetary medium, quantified by the Alfvenic Mach Number, is observed to be similar in solar maximum and minimum. It could be explained because, during solar maximum, in despite of the higher shock speeds, the Alfvenic speed of the interplanetary medium is higher than in solar minimum. I IntroductionThe interplanetary medium has a very low particle density, of about 5 Ñ ¿ , and it has a collisional mean free path of about 1 Astronomical Unit(AU) or ½ ½¼ Ñ[1]. Thus the occurrence of particle collisions is very sporadic. However, the interplanetary space is transiently disturbed by collisionless shock waves. In these shocks, the role that particle collisions make in ordinary shocks, is performed by long range Coulombian forces [1][2][3][4]. These Coulombian forces can have this very important role because the interplanetary medium is ceaseless permeated by the solar wind, a plasma resulting of the solar corona expansion and that carries with it the solar magnetic field through the solar system [1,5] Shock waves detected near the Earth's orbit, 1 AU, are mainly caused by interplanetary remnants of solar ejecta, although some types of shocks could be generated by interaction regions between slow and high speed solar wind streams [5]. Solar ejecta are coronal material expelled from the Sun, the coronal mass ejections [1,6-10] which propagate through the interplanetary medium. A shock occurs when the relative speed between a high speed stream and the background solar wind is higher than the characteristic speed of the medium (Alfvenic, magnetossonic) [1,2,3,5].Interplanetary structures can be geoeffective, causing magnetic storms, especially if an intense and long duration southward component of the magnetic field is present [6,11,12]. Because shock waves have a larger spatial extent than the interplanetary structures, it is usual that spacecrafts near Earth's orbit measure only the shock. However, the shock itself can have geoeffective effects, especially sudden impulses -increase in the H component of the geomagnetic field observed in low and mid latitudes stations, due to the intensification of Chapman-Ferraro current in the magnetopause, and magnetohydrodynamics waves and micropulsat...

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Tree ring studies are usually used to determine or verify climatic factors prevailing at a given place or region that may cause tree-ring width variations. Few studies are dedicated to the solar phenomena which may underlie these tree-ring width variations. Furthermore, it is known that some terrestrial phenomena are influenced by short-and long-time scale solar variability. An optical and computational method was set up and applied to tree samples (Araucaria angustifolia from Santa Catarina State in Southern Brazil) in order to obtain a growth ring width mean chronology. Spectral analysis is used for the search of periodicities, by maximum entropy and iterative regression methods. The results evidenced several embedded signals at periods which may be related to solar activity variations. Crosscorrelation analysis between sunspot number and tree-ring data was performed and a lag of zero year was obtained. From our work, it seems that the tropical conifer species Araucaria angustifolia may be a good choice for studies on Sun-Earth relationships and their regional effects.

The study of the physical processes that drive the variability of the Earth's climate system is one of the most fascinating and challenging topics of research today. Perhaps the largest uncertainties in our ability to predict climate change are the cloud formation process and the interaction of clouds with radiation. Here we show that in the southern Pacific Ocean cloud effects on the net radiative flux in the atmosphere are related to the intensity of the Earth's magnetic field through lower atmosphere cosmic ray effects. In the inner region of the Southern Hemisphere Magnetic Anomaly (SHMA) it is observed a cooling effect of approximately 18 W/m2 while in the outer region it is observed a heating effect of approximately 20 W/m2. The variability in the inner region of the SHMA of the net radiative flux is correlated to galactic cosmic rays (GCRs) flux observed in Huancayo, Peru (r = 0.73). It is also observed in the correlation map that the correlation increases in the inner region of the SHMA. The geomagnetic modulation of cloud effects in the net radiative flux in the atmosphere in the SHMA is, therefore, unambiguously due to GCRs and/or highly energetic solar proton particles effects.

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O número de manchas solares é o índice mais antigo da atividade solar, com observações de manchas solares estendendo-se desde 1611. Ele serve como uma medida da atividade magnética geral do Sol. Neste trabalho apresentamos uma descrição das características físicas das manchas solares, a definição do número de manchas solares, uma análise espectral do mesmo e uma reconstrução de 1000 anos.