Em busca de um novo indicador Espectroscópico do período de rotação das Estrelas do tipo solar

The study of sunspots consistently contributed to a better understanding of magnetic phenomena of the Sun, as its activity. It was found with the dynamics of sunspots that the Sun has a rotation period of twenty-seven days around your axis. With the help of Project Sun-As-A-Star that solar spectra obtained for more than thirty years we observed oscillations of both the depth of the spectral line and its equivalent width, and analysis of the return information about the characteristics of solar magnetism. It also aims to find patterns of solar magnetic activity cycle and the average period of rotation of the Sun will indicate the spectral lines that are sensitive to magnetic activity and which are not. Sensitive lines how Ti II 5381.0 Å stands as the best indicator of the solar rotation period and also shows different periods of rotation cycles of minimum and maximum magnetic activity. It is the first time we observe clearly distinct rotation periods in the different cycles. The analysis also shows that Ca II 8542.1 Å and HI 6562.0 Å indicate the cycle of magnetic activity of eleven years. Some spectral lines no indicated connection with solar activity, this result can help us search for programs planets using spectroscopic models. Data analysis was performed using the Lomb-Scargle method that makes the time series analysis for unequally spaced data. Observe different rotation periods in the cycles of magnetic activity accounts for a discussion has been debated for many decades. We verified that spectroscopy can also specify the period of stellar rotation, thus being able to generalize the method to other stars

Não-extensividade no contexto da atividade magnética solar: o problema da assimetria hemisférica

Solar activity indicators, each as sunspot numbers, sunspot area and flares, over the Sun’s photosphere are not considered to be symmetric between the northern and southern hemispheres of the Sun. This behavior is also known as the North-South Asymmetry of the different solar indices. Among the different conclusions obtained by several authors, we can point that the N-S asymmetry is a real and systematic phenomenon and is not due to random variability. In the present work, the probability distributions from the Marshall Space Flight Centre (MSFC) database are investigated using a statistical tool arises from well-known Non-Extensive Statistical Mechanics proposed by C. Tsallis in 1988. We present our results and discuss their physical implications with the help of theoretical model and observations. We obtained that there is a strong dependence between the nonextensive entropic parameter q and long-term solar variability presents in the sunspot area data. Among the most important results, we highlight that the asymmetry index q reveals the dominance of the North against the South. This behavior has been discussed and confirmed by several authors, but in no time they have given such behavior to a statistical model property. Thus, we conclude that this parameter can be considered as an effective measure for diagnosing long-term variations of solar dynamo. Finally, our dissertation opens a new approach for investigating time series in astrophysics from the perspective of non-extensivity.

Evolução da atividade cromosférica, abundância de lítio e rotação das estrelas análogas e gêmeas solares

The study of solar-type stars also includes the familiar solar analogs and twins. These objects have been one of the major research subjects in astrophysics nowadays. A direct comparison of solar activity with chromospheric activity indices for a set of stars very similar to the Sun (twins and analogs) provides an excellent opportunity to study the evolution of stellar activity on timescales of the order of the lifetime on the main sequence. This work deals with the relationship between the abundance of lithium, chromospheric activity, X-ray emission and rotation period in terms of stellar ages. We explore the influence of stellar evolution in the global properties of the stars and the aspects linked to its coronal, chromospheric and magnetic activity. Our main objective is to probe the law of decay of each of these parameters based on a sample of stars classified as well-connected as analogs stars and solar twins.

Estudos de distúrbios ionosféricos propagantes de larga escala (LSTID’S) na região equatorial durante grandes tempestades magnéticas: estudo de casos

The Ionospheric Disturbances – TIDs – are irregularities on the ionospheric plasma propagating in speeds in the order of tens to a few hundreds of meters per second. This present study detected and characterized the TIDs of LSTIDs (Large Scale Travelling Ionospheric Disturbance) type at low latitudes during intense geomagnetic storms and its propagation over the Brazilian sector. This work also shows as being the first to report systematically propagation of gravity waves over Natal. For this purpose, we used ionospheric records obtained from type of digisonde CADI (Canadiam Advanced Digital Ionosonde) located in Natal and the type DSP (Digisonde Portable Souder) located in Cachoeira Paulista, Fortaleza and São Luis, whereupon we used a dataset of 12 years collected by INPE (National Institute of Space Research). In this study, both calm days, that preceded the storms, and the geomagnetically disturbed days were related during the years 2000 and 1012, which cover a period of maximum and minimum solar activity. And it is presented the variations that happened in the electron density from region F of the ionosphere over the Brazilian sector, especially near the Equator (Natal, Fortaleza and São Luis), caused by ionospheric disturbances in the equatorial region during intense geomagnetic storms, because, as we know of the literature in this area, this phenomenon contributes positively to the emergence of LSTIDs in the auroral region, which may move to the equatorial region where a few cases have been documented and studied systematically. From the observation of signatures if TIDs in ionogram records, a study of the morphology of these events was performed and compared with the main characteristics of the wave of this phenomenon during great magnetic storms, i.e., DST <(-200 nT) and KP > 6. Thus, we obtained the main characteristics of TIDs over our region, i.e., period, vertical wavelength, phase and propagation speed, as well as the delay of these disturbances compared to the beginning of the magnetic storms to the Brazilian Sector.

Sobre a natureza dos processos físicos de aquecimento da atmosfera de estrelas do tipo solar

In the present work, we have studied the nature of the physical processes of the coronal heating, considering as basis significant samples of single and binary evolved stars, that have been achieved with the ROSAT satellite. In a total of 191 simple stars were studied, classified in the literature as giants with spectral type F, G and K. The results were compared with those obtained from 106 evolved stars of spectral type F, G and K, which belong to the spectroscopic binary systems. Accurate measurements on rotation and information about binarity were obtained from De Medeiros s catalog. We have analysed the behavior of the coronal activity in function of diverse stellar parameters. With the purpose to better clarify the profile of the stars evolution, the HR diagram was built for the two samples of stars, the single and the binary ones. The evolved traces added in the diagram were obtained from the Toulouse-Geneve code, Nascimento et al. (2000). The stars were segregated in this diagram not only in range of rotational speed but also in range of X-ray flux. Our analysis shows clearly that the single stars and the binary ones have coronal activity controlled by physical process independent on the rotation. Non magnetic processes seem to be strongly influencing the coronal heating. For the binary stars, we have also studied the behavior of the coronal emission as a function of orbital parameters, such as period and eccentricity, in which it was revealed the existence of a discontinuity in the emission of X-rays around an orbital period of 100 days. The study helped to conclude that circular orbits of the binary stars are presented as a necessary property for the existence of a higher level ofX-rays emission, suggesting that the effect of the gravitational tide has an important role in the coronal activity level. When applied the Kolmogorov-Smirnov test (KS test ) for the Vsini and FX parameters to the samples of single and binary stars, we could evidence very relevant aspects for the understanding of the mechanisms inherent to the coronal activity. For the Vsini parameter, the differences between the single stars and the binary ones for rotation over 6.3 km/s were really remarkable. We believe, therefore, that the existence of gravitational tide is, at least, one of the factors that most contribute for this behavior. About the X-rays flux, the KS test showed that the behavior of the single and the binary stars, regarding the coronal activity, comes from the same origin

Efeito do exercício físico matinal realizado sob luz solar no ciclo vigília-sono de adolescentes

The sleep onset and offset delay at adolescence in relation to childhood. Besides biological causes, some external factors as academic obligations and socialization contributes, increasing the burden of school and socialization. However, morning school schedules reduce sleep duration. Besides light strong effect, studies in humans have indicated that exercise influence circadian synchronization. To evaluate the effect of the morning exercise under sunlight on sleep-wake cycle (SWC) of adolescents, 160 high school students (11th year) were exposed to the following conditions: lesson in usual classroom (Group C), lesson in swimming pool exposed to sunlight (Group E), half of them carrying through physical activity (EE) and the other resting (EL). Each experimental group met two stages: assessment of SWC 1 week before and 1 week during the intervention, which was held in Monday and Wednesday between 7:45 and 8:30 am. In the baseline, there were applied the questionnaires "Health and Sleep" and cronotype evaluation (H & O). In addition, students were evaluated before and during the intervention by "Sleep Diary", "Karolinska Sleepiness Scale" (KSS), Psychomotor Vigilance Test (PVT) and actimetry. During the intervention, there was a delay in wake-up time on the weekend and a trend to greater sleep duration on week for the three groups. At the weekend, only the groups EE and EL increased sleep duration. There was no difference in bedtime, irregularity of sleep schedules and nap variables. The sleepiness showed a circadian pattern characterized by higher alertness levels at 11:30 am and sleepiness levels at bedtime and wake-up time on week. On weekends there were higher levels of alertness in these times. In the days of intervention, there was an increase of sleepiness at 11:30 am for groups EL and EE, which may have been caused by a relaxing effect of contact with the water of the pool. In addition, the group EE showed higher alert levels at 14:30 pm on Monday and at 8:30 am in the Wednesday, possibly caused by exercise arousal effect. The reaction time assessed through the TPV did not vary between the stages. The sleep quality improved in the three groups in the second stage, making impossible the evaluation of intervention effect. However, the sleep quality increased on Monday and Tuesday only on the group EE. From the results, it is suggested that the intervention promoted effects on the sleepiness at some day hours. In other SWC variables there were no effects, possibly due to a large SWC irregularity on weekends. Thus, the evaluation of higher weekly frequency EF is necessary, since only two days were insufficient to promote greater effect on adolescents SWC