A5030808849- Stellar, planetary, and galactic studies
- Solar and Space Plasma Dynamics
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Ionosphere and magnetosphere dynamics
- Astronomy and Astrophysical Research
- Geomagnetism and Paleomagnetism Studies
- Dust and Plasma Wave Phenomena
- Geophysics and Gravity Measurements
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Atmospheric Ozone and Climate
- Solar Radiation and Photovoltaics
- High-pressure geophysics and materials
- Fluid Dynamics and Turbulent Flows
- Astrophysics and Cosmic Phenomena
- Spectroscopy and Laser Applications
- Galaxies: Formation, Evolution, Phenomena
- Advanced Combustion Engine Technologies
- Adaptive optics and wavefront sensing
- Earthquake Detection and Analysis
- Space Exploration and Technology
- Health, Education, and Aging
- Wave and Wind Energy Systems
- Aerodynamics and Acoustics in Jet Flows
Universidade de São Paulo
2013-2022
Museu de Astronomia e Ciências Afins
2006-2021
Instituto de Astrofísica de Canarias
2001
Brazilian Institute of Geography and Statistics
1997
The Southern Photometric Local Universe Survey (S-PLUS) is imaging ~9300 deg^2 of the celestial sphere in twelve optical bands using a dedicated 0.8 m robotic telescope, T80-South, at Cerro Tololo Inter-American Observatory, Chile. telescope equipped with 9.2k by e2v detector 10 um pixels, resulting field-of-view 2 plate scale 0.55"/pixel. survey consists four main subfields, which include two non-contiguous fields high Galactic latitudes (8000 |b| > 30 deg) and areas plane bulge (for an...
Based on our previous work (Vidotto et al. 2009a), we investigate the effects wind and magnetospheric structures of weak-lined T Tauri stars due to a misalignment between axis rotation star its magnetic dipole moment vector. In such configuration, system loses axisymmetry presented in aligned case, requiring fully 3D approach. We perform numerical MHD simulations stellar winds study caused by different model parameters. The reaches periodic behavior with same rotational period star. show...
By means of self-consistent 3D MHD numerical simulations, we analyze magnetized solar-like stellar winds and their dependence on the plasma-beta parameter. We adopt in our simulations a heating parameter described by gamma, which is responsible for thermal acceleration wind. with polar magnetic field intensities ranging from 1 to 20G. show that wind structure presents characteristics are similar solar coronal The steady-state topology all cases similar, presenting configuration helmet...
By means of numerical simulations, we investigate magnetized stellar winds pre-main-sequence stars. In particular, analyze under which circumstances these stars will present elongated magnetic features (e.g., helmet streamers, slingshot prominences, etc). We focus on weak-lined T Tauri stars, as the presence tenuous accretion disk is not expected to have strong influence structure wind. show that plasma-β parameter (the ratio thermal energy densities) a decisive factor in defining...
The exact nature of eta Carinae is still an open issue. In this paper we assume a binary system to explain the strong X-ray emission, but also take into account that, near periastron and because highly eccentric orbit, wind emerging from accumulates behind shock can mimic shell-like ejection event. For process be effective, at secondary star should located between observer, solving discrepancy orbital parameters derived ground space based observations. We show as moves in its shell cools...
In this paper we present observations of η Carinae in the 1.3 mm and 7 radio continuum, during 2003.5 low excitation phase. The expected minimum light curves was confirmed at both wavelengths probably due to a decrease number UV photons available ionize gas surrounding binary system. At very well defined peak superimposed on declining flux density. It presented maximum amplitude 29 June 2003 lasted for about 10 days. We show that its origin can be free-free emission from shock formed by...
Abstract. In this paper, we present some results of previous works on Alfvén waves in a dusty plasma different astrophysical and space regions by taking into account the effect superthermal particles dispersive characteristics. We show that presence dust sensibly modify dispersion waves. The competition between damping processes kinetic cyclotron is analyzed. nonlinear evolution to chaos reviewed. Finally, discuss applications auroral region plasmas, as well stellar winds star-forming plasmas.
view Abstract Citations (34) References (50) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Mass Loss from Wolf-Rayet Stars Due to Radiation Pressure and Alfven Waves Dos Santos, L. C. ; Jatenco-Pereira, V. Opher, R. We discuss the physical mechanism that can explain observed large mass loss in luminous, (WR) stars. Interpreted classically, P Cygni line profiles imply terminal velocity of flow is about 2500 km/s. These winds are generally interpreted as...
Using a completely kinetic description to analyze wave propagation in dusty plasmas, the case of waves exactly parallel external magnetic field and Maxwellian distributions for electrons ions equilibrium is considered. A model charging process dust particles which depends on frequency inelastic collisions between used. The dispersion relation damping rates Alfvén are obtained. For numerical solutions, average value collision used as an approximation. results show that presence with variable...
Here we investigate the contribution of surface Alfven wave damping to heating solar wind in minima conditions. These waves are present regions strong inhomogeneities density or magnetic field (e. g., border between open and closed lines). Using a 3-dimensional Magnetohydrodynamics (MHD) model, calculate 1-4 radii, region interest for both acceleration coronal heating. We consider with frequencies lower than those that damped chromosphere on order dominating heliosphere. In lines, within few...
Canis Major OB1 (CMa OB1) is a Galactic stellar association with very intriguing star-formation scenario. There are more than two dozen known star clusters in its line of sight, but it not clear which ones physically associated CMa OB1. We use clustering code that employs 5-dimensional data from the Gaia DR2 catalogue to identify physical groups and obtain their astrometric parameters and, addition, we different isochrone-fitting methods estimate ages these groups. find 15 distances between...
We enter into the details of scenario Larson that there is a link between masses young stars, M0, and ambient density, ρ0: newly formed stars produce strong winds, greater ρ0, stronger wind required to blow away matter. suggest winds are Alfvén driven higher ρ0 requires flux density |$\overline \phi_{M_{0}}$|. evaluate \phi_{M_{0}}$| as function M0. study wave dissipation mechanisms: non-linear damping (L1), resonant surface (L2) turbulent (L3), show these processes can necessary create...
There are in the literature several theories to explain mass loss stellar winds. In particular, for late-type stars, some authors have proposed a wind model driven by an outward-directed flux of damped Alfven waves. The winds these stars present great amounts dust particles that, if charged, can give rise new wave modes or modify pre-existing ones. this work, we study how affect propagation waves taking into account specific damping mechanism, dust-cyclotron damping. This affects near...
In this paper we use the 7 mm and 1.3 light curves obtained during 2003.5 low excitation phase of eta Carinae system to constrain possible parameters binary orbit. To do that assumed wave emission is produced in a dense disk surrounding system; phase, which occurs close periastron, number ionizing photons decreases, producing dip radio emission. On other hand, due large eccentricity, density shock region at periastron very high plasma optically thick for free-free radiation mm, explaining...
Cool stars at giant and supergiant evolutionary phases present low-velocity high-density winds, responsible for the observed high mass-loss rates. Although presenting luminosities, radiation pressure on dust particles is not sufficient to explain wind acceleration process. Among possible solutions this still unsolved problem, Alfvén waves are, probably, most interesting their efficiency in transfering energy momentum wind. Typically, models of wave driven winds result high-velocity if they...
Abstract Electromagnetic wave fluctuations driven by temperature anisotropy in plasmas are of interest for solar flare, corona, and wind studies. We investigate the dispersion characteristics electromagnetic propagating perpendicular to uniform magnetic field which is derived using multiple particle distribution functions: Maxwellian, bi‐kappa, product bi‐kappa. The presence parallel plasma kinetic energy density exceeding a sufficient amount can lead Weibel‐like instability. A general...
view Abstract Citations (24) References (50) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observational Limits on the Coronal Hole Flow Geometry in an Alfven Wave--driven Solar Wind Jatenco-Pereira, Vera ; Opher, Reuven A model for a coronal hole geometry sun is proposed, asuming wave momentum deposition wind. For wide range of characteristic damping lengths, it shown that observational data are not satisfied by initial rapid divergence flow Hollweg (1986)...
A kinetic description is used to analyze wave propagation in dusty plasmas, taking into account the fluctuation of charge dust particles due inelastic collisions with electrons and ions. The case waves exactly parallel external magnetic field Maxwellian distributions for ions equilibrium considered, a parametric analysis dispersion relation performed. investigation emphasizes particularly effects density, radius particles, ion temperature, ratio between electron temperatures, ambient field,...
A kinetic formulation developed to analyze wave propagation in dusty plasmas, which takes into account the variation of charge dust particles due inelastic collisions with electrons and ions, is utilized study damping electrostatic waves number exactly parallel external magnetic field Maxwellian distributions for ions equilibrium. It shown that, presence dust, Langmuir region large wavelengths increased as compared conventional Landau damping. occurrence collisional charging also feature...
view Abstract Citations (15) References (47) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Power Density Spectrum Break in an Alfven Wave--driven Solar Wind Jatenco-Pereira, V. ; Opher, R. Yamamoto, L. C. situ observations of the solar wind interplanetary medium show a spectral break power density spectra. Bavassano (1990) showed that near Sun most fluctuations are propagating outward with respect to Sun, indicating observed originate from Sun....
The Hα peak intensity, velocity shift, and dispersion maps of the giant H II region NGC 604 in M33, obtained by two-dimensional high spatial resolution Fabry-Perot observations at 4.2 m William Herschel Telescope Spain, are analyzed via two-point correlation functions. whole system seems to rotate as a rigid body on scales from 50 80 pc (the largest studied scale), with period ≈ 85 Myr. We demonstrate that cloud be comprised eddies varying characteristic scale lengths which range 10 observed...
In the present study, we analyze effects of a flux Alfvén waves acting together with radiation pressure on grains as an acceleration mechanism wind late-type stars. model, simulate presence through strong damping waves, and use nonisothermal profile for temperature that is coherent grain formation theories. We examine changes in velocity wind, show if are created region 1.1 < r/r0 2.0, their will affect mass loss terminal velocity. The model applied to K5 supergiant star Betelgeuse (α Ori).
It has been shown that magnetic fields play an important role in the stability of molecular clouds, mainly perpendicularly to field direction. However, parallel direction is a serious problem still be explained. Interstellar turbulence may allow generation Alfvén waves propagate through clouds These regions also present great amounts dust particles which can give rise new wave modes, or modify pre-existing ones. The dust-cyclotron damping affects propagation near dust- cyclotron frequency....
Abstract Wave-like features recently observed in some coronal mass ejections (CMEs) have been associated with the presence of Kelvin–Helmholtz instability (KHI) low corona. Previous works found observational evidence KHI a CME; this was followed by numerical simulations order to determine magnetic field strength allowing for its existence. Here, we present first discussion formation outer corona at heliocentric distances from <?CDATA $4\,{R}_{\odot }$?> $30\,{R}_{\odot . We study separately...