Search results for "Physics::Space Physics"
showing 10 items of 357 documents
Periodic Motion for an Imperfect Solar Sail Near an Asteroid
2014
In this paper we consider the Hill 3-body problem with the extra effect of the solar radiation pressure as a model for the motion of a solar sail close to an asteroid. To model the sail’s acceleration, we include both reflectivity and absorption of the sail’s material. We describe the most relevant dynamical properties of the system for different reflectivity and absorption coefficients as well as different fixed sail orientations. We show families of periodic orbits, describe how they relate to the parameters of the sail and discuss their stability.
Bright X-Ray Flares in Orion Young Stars from COUP: Evidence for Star-Disk Magnetic Fields?
2005
We have analyzed a number of intense X-ray flares observed in the Chandra Orion Ultradeep Project (COUP), a 13 days observation of the Orion Nebula Cluster (ONC). Analysis of the flare decay allows to determine the size, peak density and magnetic field of the flaring structure. A total of 32 events (the most powerful 1% of COUP flares), have sufficient statistics for the analysis. A broad range of decay times (from 10 to 400 ks) are present in the sample. Peak flare temperatures are often very high, with half of the flares in the sample showing temperatures in excess of 100 MK. Significant sustained heating is present in the majority of the flares. The magnetic structures which are found, a…
Cornering solar radiative-zone fluctuations with KamLAND and SNO salt
2003
We update the best constraints on fluctuations in the solar medium deep within the solar Radiative Zone to include the new SNO-salt solar neutrino measurements. We find that these new measurements are now sufficiently precise that neutrino oscillation parameters can be inferred independently of any assumptions about fluctuation properties. Constraints on fluctuations are also improved, with amplitudes of 5% now excluded at the 99% confidence level for correlation lengths in the range of several hundred km. Because they are sensitive to correlation lengths which are so short, these solar neutrino results are complementary to constraints coming from helioseismology.
Constraining the neutrino magnetic moment with anti-neutrinos from the Sun
2003
We discuss the impact of different solar neutrino data on the spin-flavor-precession (SFP) mechanism of neutrino conversion. We find that, although detailed solar rates and spectra allow the SFP solution as a sub-leading effect, the recent KamLAND constraint on the solar antineutrino flux places stronger constraints to this mechanism. Moreover, we show that for the case of random magnetic fields inside the Sun, one obtains a more stringent constraint on the neutrino magnetic moment down to the level of \mu_\nu \lsim few \times 10^{-12}\mu_B, similar to bounds obtained from star cooling.
Neutrinos from the primary proton–proton fusion process in the Sun
2014
International audience; In the core of the Sun, energy is released through sequences of nuclear reactions that convert hydrogen into helium. The primary reaction is thought to be the fusion of two protons with the emission of a low-energy neutrino. These so-called pp neutrinos constitute nearly the entirety of the solar neutrino flux, vastly outnumbering those emitted in the reactions that follow. Although solar neutrinos from secondary processes have been observed, proving the nuclear origin of the Sun's energy and contributing to the discovery of neutrino oscillations, those from proton-proton fusion have hitherto eluded direct detection. Here we report spectral observations of pp neutrin…
The EUSO Data Simulation and Analysis Tree
2004
The "Extreme Universe Space Observatory - EUSO" is the first Space mission devoted to the exploration of the outermost bounds of the Universe through the investigation of the Extremely-High Energy Cosmic Rays, EECR, using the Earth atmosphere as a giant detector. The objective is to obtain a detailed description of the Cosmic Ray spectrum beyond 5×1019 eV together with a map of the arrival directions. EUSO will detect EECR looking at the streak of fluorescence light produced when such a particle interacts with the atmosphere. The signal will be detected after its propagation upward from the dark Earth atmosphere to the EUSO telescope accommodated, as external payload, on the International S…
Geometry Diagnostics of a Stellar Flare from Fluorescent X-Rays
2008
We present evidence of Fe fluorescent emission in the Chandra HETGS spectrum of the single G-type giant HR 9024 during a large flare. In analogy to solar X-ray observations, we interpret the observed Fe K$\alpha$ line as being produced by illumination of the photosphere by ionizing coronal X-rays, in which case, for a given Fe photospheric abundance, its intensity depends on the height of the X-ray source. The HETGS observations, together with 3D Monte Carlo calculations to model the fluorescence emission, are used to obtain a direct geometric constraint on the scale height of the flaring coronal plasma. We compute the Fe fluorescent emission induced by the emission of a single flaring coro…
L-Rigidity in Newtonian approximation
2008
Newtonian limit of L-Rigidity is obtained. In this formalism, L-Rigidity is reduced to steady Newtonian rigid motions in a Newtonian frame of reference in which the observer is at rest.
Unusual Optical Properties of the Dense Nonequilibrium Plasma
2006
A concise overview of new optical properties of dense nonequilibrium plasma formed on the solid state target boundary is given. In this chapter, we describe phenomena such as the third harmonic generation in the skin layer, collisionless electron heating in the high frequency skin-effect regime, absorption, and reflection and transmission of radiation by a plasma with anisotropic electron distribution.
Dynamics of anisotropic superparamagnetic particles in a precessing magnetic field.
2013
A bifurcation diagram for anisotropic magnetic particles in a precessing magnetic field is analyzed. It is found that a synchronous regime in the case of a prolate particle exists for all precession angles of the magnetic field if the frequency of field rotation is below some critical value. An oblate particle has a synchronous regime in a limited range of precession angle. To understand the flow of suspensions of these particles in precessing fields, it is essential to take into account the differing dynamics of prolate and oblate particles.