Publications

2020

Solar Orbiter: early in situ measurements
- Horbury T. S.
- Rodriguez-Pacheco J.
- Maksimovic M.
- Owen C. J.
- Angelini V.
- Bale S. D.
- Bruno R.
- Chust T.
- Evans V.
- Gomez-Herrero R.
- Ho G. C.
- Khotyaintsev Y.
- Krasnoselskikh V.
- Kretzschmar Matthieu
- Livi R.
- Lorfevre E.
- Louarn P.
- O'Brien H.
- Plettemeier D.
- Soucek J.
- Steller M.
- Stverak S.
- Travnicek P.
- Vaivads A.
- Vecchio A.
- Wimmer-Schweingruber R. F.
, 2020, 2020. Solar Orbiter was launched in February 2020 and carries four in situ instruments: the Energetic Particle Detector (EPD); the magnetometer (MAG); the Radio and Plasma Wave experiment (RPW); and the Solar Wind Analyser (SWA). Following commissioning, all instruments are operating well and taking excellent data. We give a brief overview of the in situ measurements through Orbiter's early operations, including the first perihelion at 0.52 AU. These first data reveal a rich range of phenomena including: solar energetic particle events at 0.6 AU; a coronal mass ejection measured at 0.8 AU upstream of the Earth; the first heavy ion measurements from the inner heliosphere; dust and waves throughout the inner heliosphere, including from comet ATLAS; and switchbacks from polar coronal holes at 0.5 AU. We discuss the operational strategies of the in situ payload, the plans for coordination with other missions, and the prospects for science during the coming years.
A deep insight into the ion foreshock with the help of test particle two-dimensional simulations
- Savoini Philippe
- Lembège Bertrand
Annales Geophysicae, European Geosciences Union, 2020, 38 (6), pp.1217-1235. Two-dimensional (2D) test particle simulations based on shock profiles issued from 2D full particle-in-cell (PIC) simulations are used in order to analyze the formation processes of ions back streaming within the upstream region after interacting with a quasi-perpendicular curved shock front. Two different types of simulations have been performed based on (i) a fully consistent expansion (FCE) model, which includes all self-consistent shock profiles at different times, and (ii) a homothetic expansion (HE) model in which shock profiles are fixed at certain times and artificially expanded in space. The comparison of both configurations allows one to analyze the impact of the front nonstationarity on the back-streaming population. Moreover, the role of the space charge electric field El is analyzed by either including or canceling the El component in the simulations. A detailed comparison of these last two different configurations allows one to show that this El component plays a key role in the ion reflection process within the whole quasi-perpendicular propagation range. Simulations provide evidence that the different field-aligned beam (FAB) and gyro-phase bunched (GPB) populations observed in situ are essentially formed by a Et×B drift in the velocity space involving the convective electric field Et. Simultaneously, the study emphasizes (i) the essential action of the magnetic field component on the GPB population (i.e., mirror reflection) and (ii) the leading role of the convective field Et in the FAB energy gain. In addition, the electrostatic field component El is essential for reflecting ions at high θBn angles and, in particular, at the edge of the ion foreshock around 70∘. Moreover, the HE model shows that the rate BI% of back-streaming ions is strongly dependent on the shock front profile, which varies because of the shock front nonstationarity. In particular, reflected ions appear to escape periodically from the shock front as bursts with an occurrence time period associated to the self-reformation of the shock front. (10.5194/angeo-38-1217-2020)
DOI : 10.5194/angeo-38-1217-2020
A Murine Model of a Burn Wound Reconstructed with an Allogeneic Skin Graft
- Blaise Océane
- Duchesne Constance
- Banzet Sébastien
- Rousseau A.
- Frescaline Nadira
Journal of visualized experiments : JoVE, JoVE, 2020 (162). (10.3791/61339)
DOI : 10.3791/61339
Revealing Plasma-Surface Interaction at Atmospheric Pressure: Imaging of Electric Field and Temperature inside the Targeted Material
- Slikboer Elmar
- Acharya Kishor
- Sobota Ana
- Garcia-Caurel Enric
- Guaitella Olivier
Scientific Reports, Nature Publishing Group, 2020, 10, pp.2712. The plasma-surface interaction is studied for a low temperature helium plasma jet generated at atmospheric pressure using Mueller polarimetry on an electro-optic target. The influence of the AC kHz operating frequency is examined by simultaneously obtaining images of the induced electric field and temperature of the target. The technique offers high sensitivity in the determination of the temperature variation on the level of single degrees. Simultaneously, the evolution of the electric field in the target caused by plasma-driven charge accumulation can be measured with the threshold of the order of 105 V/m. Even though a specific electro-optic crystal is used to obtain the results, they are generally applicable to dielectric targets under exposure of a plasma jet when they are of 0.5 mm thickness, have a dielectric constant greater than 4 and are at floating potential. Other techniques to examine the induced electric field in a target do not exist to the best of our knowledge, making this technique unique and necessary. The influence of the AC kHz operating frequency is important because many plasma jet designs used throughout the world operate at different frequency which changes the time between the ionization waves and hence the leftover species densities and stability of the plasma. Results for our jet show a linear operating regime between 20 and 50 kHz where the ionization waves are stable and the temperature increases linearly by 25 K. The charge deposition and induced electric fields do not increase significantly but the surface area does increase due to an extended surface propagation. Additionally, temperature mapping using a 100 ?m GaAs probe of the plasma plume area has revealed a mild heat exchange causing a heating of several degrees of the helium core while the surrounding air slightly cools. This peculiarity is also observed without plasma in the gas plume. (10.1038/s41598-020-59345-0)
DOI : 10.1038/s41598-020-59345-0
Comparative Analysis of the Vlasiator Simulations and MMS Observations of Multiple X-Line Reconnection and Flux Transfer Events
- Akhavan-Tafti M.
- Palmroth M.
- Slavin James A.
- Battarbee M.
- Ganse U.
- Grandin M.
- Le G.
- Gershman D. J.
- Eastwood Jonathan P.
- Stawarz J. E.
Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2020, 125, pp.e27410. The Vlasiator hybrid-Vlasov code was developed to investigate global magnetospheric dynamics at ion-kinetic scales. Here we focus on the role of magnetic reconnection in the formation and evolution of magnetic islands at the low-latitude magnetopause, under southward interplanetary magnetic field conditions. The simulation results indicate that (1) the magnetic reconnection ion kinetics, including the Earthward pointing Larmor electric field on the magnetospheric side of an X-point and anisotropic ion distributions, are well-captured by Vlasiator, thus enabling the study of reconnection-driven magnetic island evolution processes, (2) magnetic islands evolve due to continuous reconnection at adjacent X-points, "coalescence" which refers to the merging of neighboring islands to create a larger island, "erosion" during which an island loses magnetic flux due to reconnection, and "division" which involves the splitting of an island into smaller islands, and (3) continuous reconnection at adjacent X-points is the dominant source of magnetic flux and plasma to the outer layers of magnetic islands resulting in cross-sectional growth rates up to + 0.3 RE2/min. The simulation results are compared to the Magnetospheric Multiscale (MMS) measurements of a chain of ion-scale flux transfer events (FTEs) sandwiched between two dominant X-lines. The MMS measurements similarly reveal (1) anisotropic ion populations and (2) normalized reconnection rate ~0.18, in agreement with theory and the Vlasiator predictions. Based on the simulation results and the MMS measurements, it is estimated that the observed ion-scale FTEs may grow Earth-sized within ~10 min, which is comparable to the average transport time for FTEs formed in the subsolar region to the high-latitude magnetopause. Future simulations shall revisit reconnection-driven island evolution processes with improved spatial resolutions. (10.1029/2019JA027410)
DOI : 10.1029/2019JA027410
On the growth of the thermally modified non-resonant streaming instability
- Marret A.
- Ciardi A.
- Smets R.
- Fuchs J.
Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP): Policy P - Oxford Open Option A, 2020, 500 (2), pp.2302-2315. The cosmic rays non-resonant streaming instability is believed to be the source of substantial magnetic field amplification. In this work, we investigate the effects of the ambient plasma temperature on the instability and derive analytical expressions of its growth rate in the hot, demagnetized regime of interaction. To study its non-linear evolution, we perform hybrid-PIC simulations for a wide range of temperatures. We find that in the cold limit, about two-thirds of the cosmic rays drift kinetic energy is converted into magnetic energy. Increasing the temperature of the ambient plasma can substantially reduce the growth rate and the magnitude of the saturated magnetic field. (10.1093/mnras/staa3465)
DOI : 10.1093/mnras/staa3465
DC/LF electric field and spacecraft potential measurements in the solar wind by RPW/BIAS on Solar Orbiter
- Khotyaintsev Y. V.
- Vaivads A.
- Graham D.
- Edberg N. J. T.
- Johansson Erik P. G.
- Eriksson A. I.
- Maksimovic M.
- Bale S. D.
- Chust T.
- Krasnoselskikh V.
- Kretzschmar Matthieu
- Lorfevre E.
- Plettemeier D.
- Soucek J.
- Steller M.
- Travnicek P.
- Vecchio A.
- Horbury T. S.
- O'Brien H.
- Angelini V.
- Evans V.
- Owen C. J.
- Louarn P.
- Fedorov A.
, 2020, 2020, pp.18 pp.. The BIAS subsystem is a part of the Radio and Plasma Waves (RPW) instrument on the ESA Solar Orbiter mission. It allows sending bias current to each of the three RPW antennas. By setting the appropriate bias current the antenna potential can be shifted closer to the local plasma potential. This allows us to measure the floating potential of the spacecraft, as well as the electric field in the DC/LF frequency range with higher accuracy and lower noise level. Here we present the first results on RPW/BIAS in-flight performance based on the operations during the instrument commissioning and first months of science operations.
The Radio and Plasma Waves (RPW) Instrument on Solar Orbiter: First results.
- Maksimovic M.
- Soucek J.
- Bale S. D.
- Bonnin X.
- Chust T.
- Khotyaintsev Y.
- Kretzschmar Matthieu
- Lorfevre E.
- Plettemeier D.
- Steller M.
- Stverak S.
- Vecchio A.
- Vaivads A.
- Krasnoselskikh V.
- Krupar V.
- Alexandrova O.
- Travnicek P.
- Rucker H. O.
- Angelini V.
- Evans V.
- Fedorov A.
- Horbury T. S.
- Louarn P.
- O'Brien H.
- Owen C. J.
- Rodriguez-Pacheco J.
- Wimmer-Schweingruber R. F.
- Zouganelis Y.
, 2020, 2020. We will review the first observations and results obtained by the Radio and Plasma Waves (RPW) Instrument on the recently launched Solar Orbiter mission. RPW is designed to measure in-situ magnetic and electric fields and waves from 'DC' to a few hundreds of kHz. RPW is also capable of measuring solar radio emissions up to 16 MHz and link them to solar flares observed by the onboard remote sensing instruments. The first results concern a wide range of phenomena including: low frequency Doppler shifted ion-acoustic waves, Whistler Waves, dust impacts, Langmuir waves, shock crossings, Type III bursts, including events observed simultaneously by the Solar Orbiter Energetic Particle Detector (EPD).
Investigating Mercury's Environment with the Two-Spacecraft BepiColombo Mission
- Milillo A.
- Fujimoto M.
- Murakami G.
- Benkhoff J.
- Zender J.
- Aizawa S.
- Dósa M.
- Griton L.
- Heyner D.
- Ho G.
- Imber S. M.
- Jia X.
- Karlsson T.
- Killen R. M.
- Laurenza M.
- Lindsay S. T.
- Mckenna-Lawlor S.
- Mura A.
- Raines J. M.
- Rothery D. A.
- André N.
- Baumjohann W.
- Berezhnoy A.
- Bourdin P. A.
- Bunce E. J.
- Califano F.
- Deca Jan
- de La Fuente S.
- Dong C.
- Grava C.
- Fatemi S.
- Henri Pierre
- Ivanovski S. L.
- Jackson B. V.
- James M.
- Kallio E.
- Kasaba Y.
- Kilpua E.
- Kobayashi M.
- Langlais Benoit
- Leblanc François
- Lhotka C.
- Mangano V.
- Martindale A.
- Massetti S.
- Masters A.
- Morooka M.
- Narita Y.
- Oliveira J. S.
- Odstrcil D.
- Orsini S.
- Pelizzo M. G.
- Plainaki C.
- Plaschke F.
- Sahraoui F.
- Seki K.
- Slavin J. A.
- Vainio R.
- Wurz P.
- Barabash S.
- Carr C. M.
- Delcourt Dominique
- Glassmeier K.-H.
- Grande M.
- Hirahara M.
- Huovelin J.
- Korablev Oleg
- Kojima H.
- Lichtenegger H.
- Livi S.
- Matsuoka A.
- Moissl R.
- Moncuquet Michel
- Muinonen K.
- Quémerais Eric
- Saito Y.
- Yagitani S.
- Yoshikawa I.
- Wahlund J.-E.
Space Science Reviews, Springer Verlag, 2020, 216, pp.93. The ESA-JAXA BepiColombo mission will provide simultaneous measurements from two spacecraft, offering an unprecedented opportunity to investigate magnetospheric The BepiColombo mission to Mercury Edited A. Milillo et al. and exospheric dynamics at Mercury as well as their interactions with the solar wind, radiation , and interplanetary dust. Many scientific instruments onboard the two spacecraft will be completely, or partially devoted to study the near-space environment of Mercury as well as the complex processes that govern it. Many issues remain unsolved even after the MESSENGER mission that ended in 2015. The specific orbits of the two spacecraft, MPO and Mio, and the comprehensive scientific payload allow a wider range of scientific questions to be addressed than those that could be achieved by the individual instruments acting alone, or by previous missions. These joint observations are of key importance because many phenomena in Mercury's environment are highly temporally and spatially variable. Examples of possible coordinated observations are described in this article, analysing the required geometrical conditions, pointing, resolutions and operation timing of different BepiColombo instruments sensors. (10.1007/s11214-020-00712-8)
DOI : 10.1007/s11214-020-00712-8
Ionospheric and Magnetic Signatures of a Space Weather Event on 25–29 August 2018: CME and HSSWs
- Younas W.
- Amory-Mazaudier Christine
- Khan Majid
- Fleury Rolland
Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2020, 125 (8), pp.e2020JA027981. We present a study concerning a space weather event on 25–29 August 2018, accounting for its ionospheric and magnetic signatures at low latitudes and midlatitudes. The effects of a storm in several longitudinal sectors (Asia, Africa, America, and the Pacific) have been analyzed using various parameters such as total electron content (TEC), geomagnetic field, and column [O/N2] ratio. Positive ionospheric storms are found in all the longitudinal sectors having its maximum effects in the Asian sector, whereas the negative ionospheric storms have been observed in the summer hemisphere (Northern Hemisphere). A large decrease in [O/N2] ratio in the Northern Hemisphere is a possible cause of the observed negative storm effects. Ionospheric F2 region maximum electron density (NmF2) and TEC have shown a positive correlation during this storm. The study suggests that storm time‐generated wind does not have a uniform planetary extension and mainly affects dayside (America and Pacific) and duskside (Africa) sectors. During the space weather event, we observe an asymmetric variation of the magnetic field as a function of the longitude. On the other hand, the magnetic variations at midlatitudes are found to be symmetric in both hemispheres. A signature of the disturbance dynamo (anti‐Sq circulation) has been observed, mainly at low latitudes. We emphasize that the partial ring current (PRC), estimated by the ASYM‐H magnetic index, must also be taken into account along with the SYM‐H index for a better approximation of ionospheric currents. The study further suggests existence of several electric current cells in the ionosphere, which is consistent with the Blanc‐Richmond model. (10.1029/2020JA027981)
DOI : 10.1029/2020JA027981
Helium in the Earth's foreshock: a global Vlasiator survey
- Battarbee Markus
- Blanco-Cano Xóchitl
- Turc Lucile
- Kajdič Primož
- Johlander Andreas
- Tarvus Vertti
- Fuselier Stephen
- Trattner Karlheinz
- Alho Markku
- Brito Thiago
- Ganse Urs
- Pfau-Kempf Yann
- Akhavan-Tafti Mojtaba
- Karlsson Tomas
- Raptis Savvas
- Dubart Maxime
- Grandin Maxime
- Suni Jonas
- Palmroth Minna
Annales Geophysicae, European Geosciences Union, 2020, 38 (5), pp.1081-1099. The foreshock is a region of space upstream of the Earth's bow shock extending along the interplanetary magnetic field (IMF). It is permeated by shock-reflected ions and electrons, low-frequency waves, and various plasma transients. We investigate the extent of the He2+ foreshock using Vlasiator, a global hybrid-Vlasov simulation. We perform the first numerical global survey of the helium foreshock and interpret some historical foreshock observations in a global context. The foreshock edge is populated by both proton and helium field-aligned beams, with the proton foreshock extending slightly further into the solar wind than the helium foreshock and both extending well beyond the ultra-low frequency (ULF) wave foreshock. We compare our simulation results with Magnetosphere Multiscale (MMS) Hot Plasma Composition Analyzer (HPCA) measurements, showing how the gradient of suprathermal ion densities at the foreshock crossing can vary between events. Our analysis suggests that the IMF cone angle and the associated shock obliquity gradient can play a role in explaining this differing behaviour. We also investigate wave–ion interactions with wavelet analysis and show that the dynamics and heating of He2+ must result from proton-driven ULF waves. Enhancements in ion agyrotropy are found in relation to, for example, the ion foreshock boundary, the ULF foreshock boundary, and specular reflection of ions at the bow shock. We show that specular reflection can describe many of the foreshock ion velocity distribution function (VDF) enhancements. Wave–wave interactions deep in the foreshock cause de-coherence of wavefronts, allowing He2+ to be scattered less than protons. (10.5194/angeo-38-1081-2020)
DOI : 10.5194/angeo-38-1081-2020
A reaction mechanism for vibrationally-cold low-pressure CO2 plasmas
- Silva A. F.
- Morillo-Candas A. S.
- Tejero-Del-Caz A.
- Alves L. L.
- Guaitella Olivier
- Guerra V.
Plasma Sources Science and Technology, IOP Publishing, 2020, 29, pp.125020. The use of plasmas for CO2 utilization has been under investigation in recent years following a wave of environmental awareness. In this work, previously published experimental results on vibrationally cold CO2 plasmas are modelled to define a reaction mechanism, i.e. a set of reactions and rate coefficients validated against benchmark experiments. The model couples self-consistently the electron and heavy particle kinetics. In turn, the simulated results are validated against measurements taken in CO2 DC glow discharges in a relatively large range of experimental conditions: at pressures from 0.4 to 5 Torr, reduced electric fields ranging from 50 to 100 Td and gas flowing from 2 to 8 sccm. The model predicts the measured values of product formation (CO and O) as well as discharge power and electric field. After validation, a thorough analysis of the model's results is presented, including: electron properties, species densities, power distribution into different excitation channels and main creation and destruction mechanisms of the main species. It is shown that, although vibrational populations are low, they have a significant effect on the electron properties and thus on the electric field and conversion. Moreover, the shape of the EEDF is significantly dependent on the dissociation degree. The role of electronically excited states on CO2 dissociation is also analyzed, showing that the first electronic excited state of CO can have a beneficial or detrimental effect in further producing CO and O in the discharge. (10.1088/1361-6595/abc818)
DOI : 10.1088/1361-6595/abc818
Magnetic field fluctuation properties of coronal mass ejection-driven sheath regions in the near-Earth solar wind
- Kilpua Emilia K J
- Fontaine Dominique
- Good Simon W
- Ala-Lahti Matti
- Osmane Adnane
- Palmerio Erika
- Yordanova Emiliya
- Moissard C.
- Hadid Lina
- Janvier Miho
Annales Geophysicae, European Geosciences Union, 2020, 38, pp.999 - 1017. In this work, we investigate magnetic field fluctuations in three coronal mass ejection (CME)-driven sheath regions at 1 AU, with their speeds ranging from slow to fast. The data set we use consists primarily of high-resolution (0.092 s) magnetic field measurements from the Wind spacecraft. We analyse magnetic field fluctuation amplitudes, com-pressibility, and spectral properties of fluctuations. We also analyse intermittency using various approaches; we apply the partial variance of increments (PVIs) method, investigate probability distribution functions of fluctuations, including their skewness and kurtosis, and perform a structure function analysis. Our analysis is conducted separately for three different subregions within the sheath and one in the solar wind ahead of it, each 1 h in duration. We find that, for all cases, the transition from the solar wind ahead to the sheath generates new fluctuations, and the intermittency and com-pressibility increase, while the region closest to the ejecta leading edge resembled the solar wind ahead. The spectral indices exhibit large variability in different parts of the sheath but are typically steeper than Kolmogorov's in the inertial range. The structure function analysis produced generally the best fit with the extended p model, suggesting that turbulence is not fully developed in CME sheaths near Earth's orbit. Both Kraichnan-Iroshinikov and Kolmogorov's forms yielded high intermittency but different spectral slopes, thus questioning how well these models can describe turbulence in sheaths. At the smallest timescales investigated, the spectral indices indicate shallower than expected slopes in the dissipation range (between −2 and −2.5), suggesting that, in CME-driven sheaths at 1 AU, the energy cascade from larger to smaller scales could still be ongoing through the ion scale. Many turbulent properties of sheaths (e.g. spectral indices and compressibility) resemble those of the slow wind rather than the fast. They are also partly similar to properties reported in the terrestrial magnetosheath, in particular regarding their intermittency, compressibility, and absence of Kolmogorov's type turbulence. Our study also reveals that turbulent properties can vary considerably within the sheath. This was particularly the case for the fast sheath behind the strong and quasi-parallel shock, including a small, coherent structure embedded close to its midpoint. Our results support the view of the complex formation of the sheath and different physical mechanisms playing a role in generating fluctuations in them. (10.5194/angeo-38-999-2020)
DOI : 10.5194/angeo-38-999-2020
Solar Orbiter Observations of Waves and Structures from the Tail of Comet ATLAS
- Matteini L.
- Horbury T. S.
- Woodham L. D.
- Bale S. D.
- Hellinger P.
- Galand M. F.
- Jones G. H.
- O'Brien H.
- Evans V.
- Angelini V.
- Maksimovic M.
- Chust Thomas
- Khotyaintsev Y.
- Krasnoselskikh V.
- Kretzschmar Matthieu
- Lorfevre E.
- Plettemeier D.
- Soucek J.
- Steller M.
- Stverak S.
- Travnicek P.
- Vaivads A.
- Vecchio A.
- Bruno R.
- Fedorov A.
- Livi S. A.
- Louarn P.
- Owen C. J.
, 2020, 2020, pp.18 pp.. Comet ATLAS disintegrated into several fragments while reaching its most recent perihelion at approximately 0.25AU in April 2020. Solar Orbiter is predicted to have crossed both the ion and dust tails of the comet between 31 May and 6 June 2020, when the spacecraft was close to 0.5AU. This constituted a unique opportunity to make in situ measurements of distinct cometary fragments at such a close distance from the Sun and to study the interaction of cometary pick-up ions with the solar wind plasma. In this study, we present and discuss possible signatures of this interaction as seen in various Solar Orbiter in situ sensors (MAG, RPW, SWA). We mainly focus on properties of a wide range of both structures and low-frequency electromagnetic waves that are supposedly driven by cometary pick-up ion instabilities and intermittently observed over several days during the encounter. These include trains of phase-steepened Alfvén waves propagating in both directions along the magnetic field, sharp discontinuities and current sheets, and precessing linearly polarised waves possibly suggesting the presence of non-gyrotropic sources of heavier pick-up ions. Observed wave properties are discussed and compared with expectations from linear theory and numerical simulations.

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