76 research outputs found
Solar wind test of the de Broglie-Proca's massive photon with Cluster multi-spacecraft data
Our understanding of the universe at large and small scales relies largely on
electromagnetic observations. As photons are the messengers, fundamental
physics has a concern in testing their properties, including the absence of
mass. We use Cluster four spacecraft data in the solar wind at 1 AU to estimate
the mass upper limit for the photon. We look for deviations from Amp\`ere's
law, through the curlometer technique for the computation of the magnetic
field, and through the measurements of ion and electron velocities for the
computation of the current. We show that the upper bound for lies
between and kg, and thereby discuss
the currently accepted lower limits in the solar wind.Comment: The paper points out that actual photon mass upper limits (in the
solar wind) are too optimistic and model based. We instead perform a much
more experiment oriented measurement. This version matches that accepted by
Astroparticle Physic
Evaluation of Management System Effectiveness in the Preparation of the Aircraft for Flight in Faulty Conditions
"jats:p" Most flight delays in aviation enterprises are related to air traffic management and technical centers. This can happen for various reasons: untimely removal of defects, lack of spare parts, deficiencies in maintenance scheduling, etc. Another reason may be inefficient management in the system of preparing the aircraft for departure. The article suggests a possible option of such an assessment as well as the results obtained from the use of this methodology applied to a specific airline.
Document type: Articl
Numerical Study on the Validity of the Taylor Hypothesis in Space Plasmas
In situ heliospheric measurements allow us to resolve fluctuations as a function of frequency. A crucial point is to describe the power spectral density as a function of the wavenumber, in order to understand the energy cascade through the scales in terms of plasma turbulence theories. The most favorable situation occurs when the average wind speed is much higher than the phase speed of the plasma modes, equivalent to the fact that the fluctuations' dynamical times are much longer than their typical crossing period through the spacecraft (frozen-in Taylor approximation). Using driven compressible Hall-magneothydrodynamics simulations, in which an "imaginary" spacecraft flies across a time-evolving turbulence, here we explore the limitations of the frozen-in assumption. We find that the Taylor hypothesis is robust down to sub-proton scales, especially for flows with mean velocities typical of the fast solar wind. For slow mean flows (i.e., speeds of the order of the Alfven speed) power spectra are subject to an amplitude shift throughout the scales. At small scales, when dispersive decorrelation mechanisms become significant, the frozen-in assumption is generally violated, in particular for k-vectors almost parallel to the average magnetic field. A discussion in terms of the spacetime autocorrelation function is proposed. These results might be relevant for the interpretation of the observations, in particular for existing and future space missions devoted to very high-resolution measurements
Downstream high-speed plasma jet generation as a direct consequence of shock reformation
Shocks are one of nature's most powerful particle accelerators and have been connected to relativistic electron acceleration and cosmic rays. Upstream shock observations include wave generation, wave-particle interactions and magnetic compressive structures, while at the shock and downstream, particle acceleration, magnetic reconnection and plasma jets can be observed. Here, using Magnetospheric Multiscale (MMS) we show in-situ evidence of high-speed downstream flows (jets) generated at the Earth's bow shock as a direct consequence of shock reformation. Jets are observed downstream due to a combined effect of upstream plasma wave evolution and an ongoing reformation cycle of the bow shock. This generation process can also be applicable to planetary and astrophysical plasmas where collisionless shocks are commonly found. Several mechanisms exist for formation of jets observed in Earth's magnetosheath. Here, the authors show evidence of high-speed downstream flows generated at the Earth's bow shock as a direct consequence of shock reformation, which is different than the proposed mechanisms.Peer reviewe
Particle energization in space plasmas : towards a multi-point, multi-scale plasma observatory
This White Paper outlines the importance of addressing the fundamental science theme "How are charged particles energized in space plasmas" through a future ESA mission. The White Paper presents five compelling science questions related to particle energization by shocks, reconnection, waves and turbulence, jets and their combinations. Answering these questions requires resolving scale coupling, nonlinearity, and nonstationarity, which cannot be done with existing multi-point observations. In situ measurements from a multi-point, multi-scale L-class Plasma Observatory consisting of at least seven spacecraft covering fluid, ion, and electron scales are needed. The Plasma Observatory will enable a paradigm shift in our comprehension of particle energization and space plasma physics in general, with a very important impact on solar and astrophysical plasmas. It will be the next logical step following Cluster, THEMIS, and MMS for the very large and active European space plasmas community. Being one of the cornerstone missions of the future ESA Voyage 2050 science programme, it would further strengthen the European scientific and technical leadership in this important field.Peer reviewe
The essential role of multi-point measurements in investigations of turbulence, three-dimensional structure, and dynamics: the solar wind beyond single scale and the Taylor Hypothesis
Space plasmas are three-dimensional dynamic entities. Except under very
special circumstances, their structure in space and their behavior in time are
not related in any simple way. Therefore, single spacecraft in situ
measurements cannot unambiguously unravel the full space-time structure of the
heliospheric plasmas of interest in the inner heliosphere, in the Geospace
environment, or the outer heliosphere. This shortcoming leaves numerous central
questions incompletely answered. Deficiencies remain in at least two important
subjects, Space Weather and fundamental plasma turbulence theory, due to a lack
of a more complete understanding of the space-time structure of dynamic
plasmas. Only with multispacecraft measurements over suitable spans of spatial
separation and temporal duration can these ambiguities be resolved. We note
that these characterizations apply to turbulence across a wide range of scales,
and also equally well to shocks, flux ropes, magnetic clouds, current sheets,
stream interactions, etc. In the following, we will describe the basic
requirements for resolving space-time structure in general, using turbulence'
as both an example and a principal target or study. Several types of missions
are suggested to resolve space-time structure throughout the Heliosphere.Comment: White Paper submitted to: Decadal Survey for Solar and Space Physics
(Heliophysics) 2024-2033. arXiv admin note: substantial text overlap with
arXiv:1903.0689
Evaluation of Management System Effectiveness in the Preparation of the Aircraft for Flight in Faulty Conditions
Most flight delays in aviation enterprises are related to air traffic management and technical centers. This can happen for various reasons: untimely removal of defects, lack of spare parts, deficiencies in maintenance scheduling, etc. Another reason may be inefficient management in the system of preparing the aircraft for departure. The article suggests a possible option of such an assessment as well as the results obtained from the use of this methodology applied to a specific airline
A Model of Interconnection Between Aircraft Equipment Failures and Aircraft âStatesâ in Flight
The article presents a semiotic model of âaircraft conditionsâ in flight and multilevel structures of an aircraft. The hierarchical structure of abstract models is divided into blocks and levels that make them more compact by applying a mathematical apparatus corresponding to the goals sated. The above models were tested on the basis of statistical data on TU-154 aircraft failures for 10 years. Various aircraft functional system failures in flight were examined. The state of the aircraft is identified by normative indicators recorded in the âAircraft Technical Operation Manualâ
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