69 research outputs found
The Solar Wind Energy Flux
The solar-wind energy flux measured near the ecliptic is known to be
independent of the solar-wind speed. Using plasma data from Helios, Ulysses,
and Wind covering a large range of latitudes and time, we show that the
solar-wind energy flux is independent of the solar-wind speed and latitude
within 10%, and that this quantity varies weakly over the solar cycle. In other
words the energy flux appears as a global solar constant. We also show that the
very high speed solar-wind (VSW > 700 km/s) has the same mean energy flux as
the slower wind (VSW < 700 km/s), but with a different histogram. We use this
result to deduce a relation between the solar-wind speed and density, which
formalizes the anti-correlation between these quantities.Comment: 12 pages, 5 figure
Electron density distribution and solar plasma correction of radio signals using MGS, MEX and VEX spacecraft navigation data and its application to planetary ephemerides
The Mars Global Surveyor (MGS), Mars Express (MEX), and Venus Express (VEX)
experienced several superior solar conjunctions. These conjunctions cause
severe degradations of radio signals when the line of sight between the Earth
and the spacecraft passes near to the solar corona region. The primary
objective of this work is to deduce a solar corona model from the spacecraft
navigation data acquired at the time of solar conjunctions and to estimate its
average electron density. The corrected or improved data are then used to fit
the dynamical modeling of the planet motions, called planetary ephemerides. We
analyzed the radio science raw data of the MGS spacecraft using the orbit
determination software GINS. The range bias, obtained from GINS and provided by
ESA for MEX and VEX, are then used to derive the electron density profile.
These profiles are obtained for different intervals of solar distances: from
12Rs to 215Rs for MGS, 6Rs to 152Rs for MEX, and form 12Rs to 154Rs for VEX.
They are acquired for each spacecraft individually, for ingress and egress
phases separately and both phases together, for different types of solar winds
(fast, slow), and for solar activity phases (minimum, maximum). We compared our
results with the previous estimations that were based on in situ measurements,
and on solar type III radio and radio science studies made at different phases
of solar activity and at different solar wind states. Our results are
consistent with estimations obtained by these different methods. Moreover,
fitting the planetary ephemerides including complementary data that were
corrected for the solar corona perturbations, noticeably improves the
extrapolation capability of the planetary ephemerides and the estimation of the
asteroids masses.Comment: Accepted for publication in A&
Heating of the solar wind with electron and proton effects
We examine the effects of including effects of both protons and electrons on the heating of the fast solar wind through two different approaches. In the first approach, we incorporate the electron temperature in an MHD turbulence transport model for the solar wind. In the second approach, we adopt more empirically based methods by analyzing the measured proton and electron temperatures to calculate the heat deposition rates. Overall, we conclude that incorporating separate proton and electron temperatures and heat conduction effects provides an improved and more complete model of the heating of the solar wind
Polarization entangled photon-pair source based on a type-II PPLN waveguide emitting at a telecom wavelength
We report the realization of a fiber coupled polarization entangled
photon-pair source at 1310 nm based on a birefringent titanium in-diffused
waveguide integrated on periodically poled lithium niobate. By taking advantage
of a dedicated and high-performance setup, we characterized the quantum
properties of the pairs by measuring two-photon interference in both
Hong-Ou-Mandel and standard Bell inequality configurations. We obtained, for
the two sets of measurements, interference net visibilities reaching nearly
100%, which represent important and competitive results compared to similar
waveguide-based configurations already reported. These results prove the
relevance of our approach as an enabling technology for long-distance quantum
communication.Comment: 13 pages, 4 figures, to appear in New Journal of Physic
High-quality polarization entanglement state preparation and manipulation in standard telecommunication channels
We report a novel and simple approach for generating near-perfect quality
polarization entanglement in a fully guided-wave fashion. Both deterministic
pair separation into two adjacent telecommunication channels and the paired
photons' temporal walk-off compensation are achieved using standard fiber
components. Two-photon interference experiments are performed, both for
quantitatively demonstrating the relevance of our approach, and for
manipulating the produced state between bosonic and fermionic symmetries. The
compactness, versatility, and reliability of this configuration makes it a
potential candidate for quantum communication applications.Comment: 6 figure
Total Electron Temperature Derived from Quasi-Thermal Noise Spectroscopy In the Pristine Solar Wind: Parker Solar Probe Observations
The Quasi-thermal noise (QTN) technique is a reliable tool to yield accurate
measurements of the electron parameters in the solar wind. We apply this method
on Parker Solar Probe (PSP) observations to derive the total electron
temperature () from the linear fit of the high-frequency part of the QTN
spectra acquired by the RFS/FIELDS instrument, and present a combination of
12-day period of observations around each perihelion from Encounter One (E01)
to Ten (E10) (with E08 not included) with the heliocentric distance varying
from about 13 to 60 solar radii (). We find that the total electron
temperature decreases with the distance as , which is much
slower than adiabatic. The extrapolated based on PSP observations is
consistent with the exospheric solar wind model prediction at 10
, Helios observations at 0.3 AU and Wind observations at 1 AU.
Also, , extrapolated back to 10 , is almost the same as the
strahl electron temperature (measured by SPAN-E) which is considered to
be closely related to or even almost equal to the coronal electron temperature.
Furthermore, the radial profiles in the slower solar wind (or flux tube
with larger mass flux) are steeper than those in the faster solar wind (or flux
tube with smaller mass flux). More pronounced anticorrelated - is
observed when the solar wind is slower and closer to the Sun.Comment: 10 pages, 7 figures, and Astronomy & Astrophysics Accepte
Analysis of Elliptically Polarized Maximally Entangled States for Bell Inequality Tests
When elliptically polarized maximally entangled states are considered, i.e.,
states having a non random phase factor between the two bipartite polarization
components, the standard settings used for optimal violation of Bell
inequalities are no longer adapted. One way to retrieve the maximal amount of
violation is to compensate for this phase while keeping the standard Bell
inequality analysis settings. We propose in this paper a general theoretical
approach that allows determining and adjusting the phase of elliptically
polarized maximally entangled states in order to optimize the violation of Bell
inequalities. The formalism is also applied to several suggested experimental
phase compensation schemes. In order to emphasize the simplicity and relevance
of our approach, we also describe an experimental implementation using a
standard Soleil-Babinet phase compensator. This device is employed to correct
the phase that appears in the maximally entangled state generated from a
type-II nonlinear photon-pair source after the photons are created and
distributed over fiber channels.Comment: 8 page
Wind/WAVES observations of Auroral Kilometric Radiation: automated burst detection and Terrestrial Solar Wind - Magnetosphere coupling effects
Auroral Kilometric Radiation (AKR) is the strongest terrestrial radio emission, and emanates from the same electron acceleration regions from which particles precipitate into the ionosphere, exciting the aurorae and other phenomena. As such, AKR is a barometer for the state of solar wind - magnetosphere - ionosphere coupling. AKR is anisotropically beamed in a hollow cone from a source region generally found at nightside local times, meaning that a single source region cannot be viewed from all local times in the magnetosphere. In radio data such as dynamic spectra, AKR is frequently observed simultaneously to other radio emissions which can have a similar intensity and frequency range, making it difficult to automatically detect. Building on a previously published pipeline to extract AKR emissions from Wind/WAVES data, in this paper a novel automated AKR burst detection technique is presented and applied again to Wind/WAVES data. Over a five year interval, about 5000 AKR bursts are detected with median burst length ranging from about 30-60 minutes. During detected burst windows, higher solar wind velocity is observed, and the interplanetary magnetic field (IMF) clock angle is observed to tend towards BZ<0, BY<0, when compared with the entire statistical interval. Additionally, higher geomagnetic activity is observed during burst windows at polar, high and equatorial latitudes
Measuring Solar Abundances
This is the rapporteur paper of Working Group 2 on Measuring Solar Abundances. The working group presented and discussed the different observations and methods for obtaining the elemental and isotopic composition of the Sun, and critically reviewed their results and the accuracies thereof. Furthermore, a few important yet unanswered questions were identified, and the potential of future missions to provide answers was assessed
A transonic collisionless model of the solar wind
Because of the semi-collisional nature of the solar wind, the collisionless
or exospheric approach as well as the hydrodynamic one are both inaccurate.
However, the advantage of simplicity makes them useful for enlightening some
basic mechanisms of solar wind acceleration. Previous exospheric models have
been able to reproduce winds that were already nearly supersonic at the
exobase, the altitude above which there are no collisions. In order to allow
transonic solutions, a lower exobase has to be considered, in which case the
protons are experiencing a non-monotonic potential energy profile. This is done
in the present work. In this model, the electron velocity distribution in the
corona is assumed non-thermal. Parametric results are presented and show that
the high acceleration obtained does not depend on the details of the
non-thermal distributions. This acceleration seems, therefore, to be a robust
result produced by the presence of a sufficient number of suprathermal
electrons. A method for improving the exospheric description is also given,
which consists in mapping particle orbits in terms of their invariants of
motion.Comment: 18 pages, 18 figures, accepted for publication in The Astrophysical
Journal (1 May 2004
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