The role of empirical space-weather models (in a world of physics-based numerical simulations)

Advanced forecasting of space weather requires prediction of near-Earth solar-wind conditions on the basis of remote solar observations. This is typically achieved using numerical magnetohydrodynamic models initiated by photospheric magnetic field observations. The accuracy of such forecasts is being continually improved through better numerics, better determination of the boundary conditions and better representation of the underlying physical processes. Thus it is not unreasonable to conclude that simple, empirical solar-wind forecasts have been rendered obsolete. However, empirical models arguably have more to contribute now than ever before. In addition to providing quick, cheap, independent forecasts, simple empirical models aid in numerical model validation and verification, and add value to numerical model forecasts through parameterization, uncertainty estimation and ‘downscaling’ of sub-grid processes

Clustering of magnetic reconnection exhausts in the solar wind: An automated detection study

CONTEXT: Magnetic reconnection is a fundamental process in astrophysical plasmas that enables the dissipation of magnetic energy at kinetic scales. Detecting this process in situ is therefore key to furthering our understanding of energy conversion in space plasmas. However, reconnection jets typically scale from seconds to minutes in situ, and as such, finding them in the decades of data provided by solar wind missions since the beginning of the space era is an onerous task. AIMS: In this work, we present a new approach for automatically identifying reconnection exhausts in situ in the solar wind. We apply the algorithm to Solar Orbiter data obtained while the spacecraft was positioned at between 0.6 and 0.8 AU and perform a statistical study on the jets we detect. METHODS: The method for automatic detection is inspired by the visual identification process and strongly relies on the Walén relation. It is enhanced through the use of Bayesian inference and physical considerations to detect reconnection jets with a consistent approach. RESULTS: Applying the detection algorithm to one month of Solar Orbiter data near 0.7 AU, we find an occurrence rate of seven jets per day, which is significantly higher than in previous studies performed at 1 AU. We show that they tend to cluster in the solar wind and are less likely to occur in the tenuous solar wind (< 10 cm−3 near 0.7 AU). We discuss why the source and the degree of Alfvénicity of the solar wind might have an impact on magnetic reconnection occurrence. CONCLUSIONS: By providing a tool to quickly identify potential magnetic reconnection exhausts in situ, we pave the way for broader statistical studies on magnetic reconnection in diverse plasma environments

Single-spacecraft techniques for shock parameters estimation: A systematic approach

Spacecraft missions provide the unique opportunity to study the properties of collisionless shocks utilising in situ measurements. In the past years, several diagnostics have been developed to address key shock parameters using time series of magnetic field (and plasma) data collected by a single spacecraft crossing a shock front. A critical aspect of such diagnostics is the averaging process involved in the evaluation of upstream/downstream quantities. In this work, we discuss several of these techniques, with a particular focus on the shock obliquity (defined as the angle between the upstream magnetic field and the shock normal vector) estimation. We introduce a systematic variation of the upstream/downstream averaging windows, yielding to an ensemble of shock parameters, which is a useful tool to address the robustness of their estimation. This approach is first tested with a synthetic shock dataset compliant with the Rankine-Hugoniot jump conditions for a shock, including the presence of noise and disturbances. We then employ self-consistent, hybrid kinetic shock simulations to apply the diagnostics to virtual spacecraft crossing the shock front at various stages of its evolution, highlighting the role of shock-induced fluctuations in the parameters’ estimation. This approach has the strong advantage of retaining some important properties of collisionless shock (such as, for example, the shock front microstructure) while being able to set a known, nominal set of shock parameters. Finally, two recent observations of interplanetary shocks from the Solar Orbiter spacecraft are presented, to demonstrate the use of this systematic approach to real events of shock crossings. The approach is also tested on an interplanetary shock measured by the four spacecraft of the Magnetospheric Multiscale (MMS) mission. All the Python software developed and used for the diagnostics (SerPyShock) is made available for the public, including an example of parameter estimation for a shock wave recently observed in-situ by the Solar Orbiter spacecraft.</p

Gesture and naming therapy for people with severe aphasia: a group study

In this study, the authors (a) investigated whether a group of people with severe aphasia could learn a vocabulary of pantomime gestures through therapy and (b) compared their learning of gestures with their learning of words. The authors also examined whether gesture therapy cued word production and whether naming therapy cued gestures

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

Slow Solar Wind Connection Science during Solar Orbiter’s First Close Perihelion Passage

The Slow Solar Wind Connection Solar Orbiter Observing Plan (Slow Wind SOOP) was developed to utilize the extensive suite of remote-sensing and in situ instruments on board the ESA/NASA Solar Orbiter mission to answer significant outstanding questions regarding the origin and formation of the slow solar wind. The Slow Wind SOOP was designed to link remote-sensing and in situ measurements of slow wind originating at open–closed magnetic field boundaries. The SOOP ran just prior to Solar Orbiter’s first close perihelion passage during two remote-sensing windows (RSW1 and RSW2) between 2022 March 3–6 and 2022 March 17–22, while Solar Orbiter was at respective heliocentric distances of 0.55–0.51 and 0.38–0.34 au from the Sun. Coordinated observation campaigns were also conducted by Hinode and IRIS. The magnetic connectivity tool was used, along with low-latency in situ data and full-disk remote-sensing observations, to guide the target pointing of Solar Orbiter. Solar Orbiter targeted an active region complex during RSW1, the boundary of a coronal hole, and the periphery of a decayed active region during RSW2. Postobservation analysis using the magnetic connectivity tool, along with in situ measurements from MAG and SWA/PAS, showed that slow solar wind originating from two out of three of the target regions arrived at the spacecraft with velocities between ∼210 and 600 km s−1. The Slow Wind SOOP, despite presenting many challenges, was very successful, providing a blueprint for planning future observation campaigns that rely on the magnetic connectivity of Solar Orbiter

Anisotropy of solar wind turbulence

As well as being of fundamental interest, understanding plasma turbulence is important for many areas of astrophysics and space physics that remain to be fully understood, such as accretion disk dynamics, the origin of cosmic rays and coronal heating. The anisotropy with respect to the magnetic fi eld is central to understanding plasma turbulence, but this has only recently started to be measured in detail. The solar wind provides a unique opportunity to study this anisotropy due to the range of high precision in situ measurements available. In this thesis, the anisotropy of solar wind turbulence is measured using data from the multi-spacecraft Cluster mission. At all scales measured, the fluctuations are found to be spatially anisotropic: elongated along the direction of the magnetic field. The scaling of the turbulence is also anisotropic, with a steeper spectral index in the direction parallel to the local magnetic fi eld. This is consistent with the fluctuations being in critical balance: having approximately equal linear wave timescales and nonlinear eddy decay timescales. At large scales, the anisotropy of the density and parallel magnetic fi eld fluctuations follows that of the perpendicular Alfvénic turbulence, in agreement with passive scalar theory. One puzzling result, however, is the scaling of the parallel magnetic field at small scales, which does not follow theoretical expectations. For the fi rst time, the technique used to measure the anisotropy of solar wind turbulence is applied to turbulence in reduced magnetohydrodynamic simulations. Again, the anisotropic scaling is seen, which is in agreement with critical balance predictions. It is also shown that when measuring the anisotropy with respect to the global, rather than local magnetic field, the anisotropic scaling cannot always be properly measured, which explains the previous apparently contradictory measurements in the literature.EThOS - Electronic Theses Online ServiceSTFC (plus travel to conferences funded by many other bodies)GBUnited Kingdo

STELLA — In situ Investigations of the Very Local Interstellar Medium. Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033 white paper e-id. 433

International audienceVoyager 1 & 2, Ulysses, Cassini, and IBEX have shown that the interaction between interstellar medium and solar wind is much more complex and involved than previously believed. This whitepaper proposes to study this interaction in situ at the heliospheric boundaries and to explore the very local interstellar medium beyond with new instrumentation that is built to investigate this final frontier

STELLA — In situ Investigations of the Very Local Interstellar Medium. Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033 white paper e-id. 433

International audienceVoyager 1 & 2, Ulysses, Cassini, and IBEX have shown that the interaction between interstellar medium and solar wind is much more complex and involved than previously believed. This whitepaper proposes to study this interaction in situ at the heliospheric boundaries and to explore the very local interstellar medium beyond with new instrumentation that is built to investigate this final frontier

STELLA — In situ Investigations of the Very Local Interstellar Medium. Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033 white paper e-id. 433

International audienceVoyager 1 & 2, Ulysses, Cassini, and IBEX have shown that the interaction between interstellar medium and solar wind is much more complex and involved than previously believed. This whitepaper proposes to study this interaction in situ at the heliospheric boundaries and to explore the very local interstellar medium beyond with new instrumentation that is built to investigate this final frontier