BV technique for investigating 1-D interfaces

To investigate the internal structure of the magnetopause with spacecraft data, it is crucial to be able to determine its normal direction and to convert the measured time series into spatial profiles. We propose here a new single-spacecraft method, called the BV method, to reach these two objectives. Its name indicates that the method uses a combination of the magnetic field (B) and velocity (V) data. The method is tested on simulation and Cluster data, and a short overview of the possible products is given. We discuss its assumptions and show that it can bring a valuable improvement with respect to previous methods.Comment: submitted to JG

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

HelioSwarm: A Multipoint, Multiscale Mission to Characterize Turbulence

HelioSwarm (HS) is a NASA Medium-Class Explorer mission of the Heliophysics Division designed to explore the dynamic three-dimensional mechanisms controlling the physics of plasma turbulence, a ubiquitous process occurring in the heliosphere and in plasmas throughout the universe. This will be accomplished by making simultaneous measurements at nine spacecraft with separations spanning magnetohydrodynamic and sub-ion spatial scales in a variety of near-Earth plasmas. In this paper, we describe the scientific background for the HS investigation, the mission goals and objectives, the observatory reference trajectory and instrumentation implementation before the start of Phase B. Through multipoint, multiscale measurements, HS promises to reveal how energy is transferred across scales and boundaries in plasmas throughout the universe

Magnetospheric MultiScale observations of energetic ion acceleration at multiple turbulent jet fronts

International audiencePlasma jets in astrophysical plasma frequently lead to the formation of kinetic-scale boundaries, often referred to as jet fronts, which separate the hot jetting from the colder ambient plasma ahead of the jet. In the Earth's magnetotail, jets fronts are often associated with reconnection and are observed by spacecraft as a steep increase in the component of the magnetic field normal to the current sheet, accompanied by a plasma temperature increase and density decrease. Jet fronts play an important role in ion acceleration in the magnetotail. However, how exactly the different ion species get accelerated is still unclear. Recent high-resolution measurements of ion distribution functions in the magnetotail from the Magnetospheric MultiScale (MMS) spaceraft allow now for the first time to study the acceleration mechanisms in detail and their dependence on the ion species. Here present an event with multiple turbulent jet fronts observed by MMS in the magnetotail. Such fronts have also been recently reproduced by Particle-In-Cell numerical simulations. We investigate the acceleration of protons and heavier ions due to the interaction of fronts and the role of jets' turbulence for the energization

THOR Ion Mass Spectrometer (IMS)

International audienceTurbulence Heating ObserveR (THOR) is the first mission ever flown in space dedicated to plasma turbulence. The Ion Mass Spectrometer (IMS) onboard THOR will provide the first high-time resolution measurements of mass-resolved ions in near-Earth space, focusing on hot ions in the foreshock, shock and magnetosheath turbulent regions. These measurements are required to study how kinetic-scale turbulent fluctuations heat and accelerate different ion species. IMS will measure the full three-dimensional distribution functions of main ion species (H , He , O ) in the energy range 10 eV/q to 30 keV/q with energy resolution DE/E down to 10% and angular resolution down to 11.25˚ . The time resolution will be 150 ms for O , 300 ms for He and 1s for O , which correspond to ion scales in the the foreshock, shock and magnetosheath regions. Such high time resolution is achieved by mounting four identical IMS units phased by 90˚ in the spacecraft spin plane. Each IMS unit combines a top-hat electrostatic analyzer with deflectors at the entrance together with a time-of-flight section to perform mass selection. Adequate mass-per-charge resolution (M/q)/(DeltaM/q) (>= 8 for He and >= 3 for O ) is obtained through a 6 cm long Time-of-Flight (TOF) section. IMS electronics includes a fast sweeping high voltage board that is required to make measurements at high cadence. Ion detection includes Micro Channel Plates (MCPs) combined with Application-Specific Integrated Circuits (ASICs) for charge amplification and discrimination and a discrete Time-to-Amplitude Converter (TAC) to determine the ion time of flight. A processor board will be used to for ion events formatting and will interface with the Particle Processing Unit (PPU), which will perform data processing for THOR particle detectors. The IMS instrument is being designed and will be built and calibrated by an international consortium of scientific institutes from France, USA, Germany and Japan and Switzerland

The physics of magnetic reconnection onset at the subsolar magnetopause: MMS observations

International audienceMagnetic reconnection is a fundamental process occurring in thin current sheets where a change in the magnetic field topology leads to fast magnetic energy conversion into charged particles energy. A key yet poorly understood aspect is how reconnection is initiated in the diffusion region by microphysical processes occurring at electron scales, the so-called onset problem. Reconnection onset leads to the energization of particles around reconnection sites, yet the exact energization mechanisms are also not yet fully understood. Simulations have provided some suggestions on the mechanisms responsible for onset and particle energization, however direct observations have been scarce so far. The four-spacecraft Magnetospheric Multiscale Mission (NASA/MMS) has been launched in March 2015 and allows, for the first time, in-situ observations of reconnection diffusion regions with adequate resolution to study electron scales. Here we present MMS observations in diffusion regions at the subsolar magnetopause and we investigate the conditions for reconnection onset. We select a few events with multiple crossings of the magnetopause current sheet for which signatures of absence of reconnection are rapidly followed by signatures of reconnection, and compare the measured electric field with the electric field due to both kinetic effects (electron pressure tensor, electron inertia terms) and to anomalous resistivity associated to different wave modes (e.g. lower hybrid waves, whistler waves, etc.). We also analyze electron distribution functions to study the mechanisms of electron energization in the diffusion region

Magnetospheric MultiScale observations of energetic ion acceleration at multiple turbulent jet fronts

International audiencePlasma jets in astrophysical plasma frequently lead to the formation of kinetic-scale boundaries, often referred to as jet fronts, which separate the hot jetting from the colder ambient plasma ahead of the jet. In the Earth's magnetotail, jets fronts are often associated with reconnection and are observed by spacecraft as a steep increase in the component of the magnetic field normal to the current sheet, accompanied by a plasma temperature increase and density decrease. Jet fronts play an important role in ion acceleration in the magnetotail. However, how exactly the different ion species get accelerated is still unclear. Recent high-resolution measurements of ion distribution functions in the magnetotail from the Magnetospheric MultiScale (MMS) spaceraft allow now for the first time to study the acceleration mechanisms in detail and their dependence on the ion species. Here present an event with multiple turbulent jet fronts observed by MMS in the magnetotail. Such fronts have also been recently reproduced by Particle-In-Cell numerical simulations. We investigate the acceleration of protons and heavier ions due to the interaction of fronts and the role of jets' turbulence for the energization

THOR: a candidate ESA mission to explore turbulent energy dissipation and particle energization in space plasmas

International audienc

THOR - Turbulence Heating ObserveR

International audienc

Turbulent energy dissipation in thin reconnecting current sheets

International audienc