29 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
Turbulence-driven ion beams in the magnetospheric Kelvin-Helmholtz instability
The description of the local turbulent energy transfer via a heuristic proxy derived from the third-order moment scaling law, and the high-resolution ion distributions measured by the Magnetospheric Multiscale mission, together provide a formidable tool to explore the cross-scale connection between the ïŹuid-scale energy cascade and plasma processes at sub-ion scales. Using magnetospheric boundary layers measurements, we show that when the small-scale energy transfer is dominated by AlfvĂ©nic, correlated velocity and magnetic ïŹeld ïŹuctuations, beams of accelerated particles are more likely observed. Here, for the ïŹrst time we report observations suggesting the nonlinear wave-particle interaction as one possible mechanism for the energy dissipation in space plasmas
Three-dimensional modelling of the shock-turbulence interaction
The complex interaction between shocks and plasma turbulence is extremely
important to address crucial features of energy conversion in a broad range of
astrophysical systems. We study the interaction between a supercritical,
perpendicular shock and pre-existing, fully-developed plasma turbulence,
employing a novel combination of magnetohydrodynamic (MHD) and small-scale,
hybrid-kinetic simulations where a shock is propagating through a turbulent
medium. The variability of the shock front in the unperturbed case and for two
levels of upstream fluctuations is addressed.We find that the behaviour of
shock ripples, i.e., shock surface fluctuations with short (a few ion skin
depths, ) wavelengths, is modified by the presence of pre-existing
turbulence, which also induces strong corrugations of the shock front at larger
scales. We link this complex behaviour of the shock front and the shock
downstream structuring with the proton temperature anisotropies produced in the
shock-turbulence system. Finally, we put our modelling effort in the context of
spacecraft observations, elucidating the role of novel cross-scale,
multi-spacecraft measurements in resolving shock front irregularities at
different scales. These results are relevant for a broad range of astrophysical
systems characterised by the presence of shock waves interacting with plasma
turbulence.Comment: Submitted to MNRA
The Persistent Mystery of Collisionless Shocks
Collisionless shock waves are one of the main forms of energy conversion in
space plasmas. They can directly or indirectly drive other universal plasma
processes such as magnetic reconnection, turbulence, particle acceleration and
wave phenomena. Collisionless shocks employ a myriad of kinetic plasma
mechanisms to convert the kinetic energy of supersonic flows in space to other
forms of energy (e.g., thermal plasma, energetic particles, or Poynting flux)
in order for the flow to pass an immovable obstacle. The partitioning of energy
downstream of collisionless shocks is not well understood, nor are the
processes which perform energy conversion. While we, as the heliophysics
community, have collected an abundance of observations of the terrestrial bow
shock, instrument and mission-level limitations have made it impossible to
quantify this partition, to establish the physics within the shock layer
responsible for it, and to understand its dependence on upstream conditions.
This paper stresses the need for the first ever spacecraft mission specifically
designed and dedicated to the observation of both the terrestrial bow shock as
well as Interplanetary shocks in the solar wind.Comment: White paper submitted to the Decadal Survey for Solar and Space
Physics (Heliophysics) 2024-2033; 9 pages, 4 figure
Sign Singularity of the Local Energy Transfer in Space Plasma Turbulence
In weakly collisional space plasmas, the turbulent cascade provides most of the energy that is dissipated at small scales by various kinetic processes. Understanding the characteristics of such dissipative mechanisms requires the accurate knowledge of the fluctuations that make energy available for conversion at small scales, as different dissipation processes are triggered by fluctuations of a different nature. The scaling properties of different energy channels are estimated here using a proxy of the local energy transfer, based on the third-order moment scaling law for magnetohydrodynamic turbulence. In particular, the sign-singularity analysis was used to explore the scaling properties of the alternating positive-negative energy fluxes, thus providing information on the structure and topology of such fluxes for each of the different type of fluctuations. The results show the highly complex geometrical nature of the flux, and that the local contributions associated with energy and cross-helicity non-linear transfer have similar scaling properties. Consequently, the fractal properties of current and vorticity structures are similar to those of the Alfvenic fluctuations
The Search-Coil Magnetometer onboard the ESA JUICE mission
International audienceThe JUpiter ICy moons Explorer (JUICE) mission is the first large-class (L1) mission in ESA Cosmic Vision. JUICE is planned for launch in 2022 with arrival at Jupiter in 2029 and will spend at least four years making detailed observations of Jupiter's magnetosphere and of three of its largest moons (Ganymede, Callisto and Europa). The Radio and Plasma Wave Investigation (RPWI) consortium will carry the most advanced set of electric and magnetic fields sensors ever flown in Jupiter's magnetosphere, which will allow to characterize the radio emission and plasma wave environment of Jupiter and its icy moons. Here we present the scientific objectives and the technical features of the Search Coil Magnetometer (SCM) of RPWI. SCM will provide for the first time high-quality three-dimensional measurements of magnetic field fluctuations' vector in the frequency range 0.1 Hz - 20 kHz within Jupiter's magnetosphere. High sensitivity (~ 4 fT / âHz at 4 kHz) will be assured by combining an optimized (20 cm long) magnetic transducer with a low-noise (4 nV / âHz ) ASICs pre-amplifier for the front-end electronics. Perturbations by the spacecraft are strongly reduced by accommodating SCM more at ~ 10 m away from the spacecraft on the JUICE magnetometer boom. The combination of high sensitivity and high cleanliness of SCM measurements will allow unpreceded studies of waves and turbulence down to kinetic scales, in particular in key regions such as the magnetopause, the auroral region and the magnetotail current sheet of Ganymede's magnetosphere. This will lead to important advances in understanding wave-particle interaction and particle energization mechanisms in Jupiter's magnetosphere
Editorial: The Role of Turbulence in the Solar Wind, Magnetosphere, Ionosphere Dynamics
International audienc
Proton and heavy ion acceleration by electromagnetic fluctuations in the Earthâs magnetotail
International audienc
Proton and heavy ion acceleration by electromagnetic fluctuations in the Earthâs magnetotail
International audienc
Cluster observations of energetic electron acceleration within earthward reconnection jet and associated magnetic flux rope
International audienc