Publications

2019

Physics research on the TCV tokamak facility: from conventional to alternative scenarios and beyond
- Coda S.
- Agostini M.
- Albanese R.
- Alberti S.
- Alessi E.
- Allan S.
- Allcock J.
- Ambrosino R.
- Anand H.
- Andrèbe Y.
- Arnichand H.
- Auriemma F.
- Ayllon-Guerola J.M.
- Bagnato F.
- Ball J.
- Baquero-Ruiz M.
- Beletskii A.A.
- Bernert M.
- Bin W.
- Blanchard P.
- Blanken T.C.
- Boedo J.A.
- Bogar O.
- Bolzonella T.
- Bombarda F.
- Bonanomi N.
- Bouquey F.
- Bowman C.
- Brida D.
- Bucalossi J.
- Buermans J.
- Bufferand H.
- Buratti P.
- Calabró G.
- Calacci L.
- Camenen Y.
- Carnevale D.
- Carpanese F.
- Carr M.
- Carraro L.
- Casolari A.
- Causa F.
- Čeřovský J.
- Chellaï O.
- Chmielewski P.
- Choi D.
- Christen N.
- Ciraolo G.
- Cordaro L.
- Costea S.
- Cruz N.
- Czarnecka A.
- Molin A. Dal
- David P.
- Decker J.
- Oliveira H. De
- Douai D.
- Dreval M.B.
- Dudson B.
- Dunne M.
- Duval B.P.
- Eich T.
- Elmore S.
- Embréus O.
- Esposito B.
- Faitsch M.
- Farník M.
- Fasoli A.
- Fedorczak N.
- Felici F.
- Feng S.
- Feng X.
- Ferro G.
- Février O.
- Ficker O.
- Fil Alexandre
- Fontana M.
- Frassinetti L.
- Furno I.
- Gahle D.S.
- Galassi D.
- Ga\lązka K.
- Gallo A.
- Galperti C.
- Garavaglia S.
- Garcia J.
- Garcia-Muñoz M.
- Garrido A.J.
- Garrido I.
- Gath J.
- Geiger B.
- Giruzzi G.
- Gobbin M.
- Goodman T.P.
- Gorini G.
- Gospodarczyk M.
- Granucci G.
- Graves J.P.
- Gruca M.
- Gyergyek T.
- Hakola A.
- Happel T.
- Harrer G.F.
- Harrison J.
- Havlíčková E.
- Hawke J.
- Henderson S.
- Hennequin P.
- Hesslow L.
- Hogeweij D.
- Hogge J.-Ph.
- Hopf C.
- Hoppe M.
- Horáček J.
- Huang Z.
- Hubbard A.
- Iantchenko A.
- Igochine V.
- Innocente P.
- Schrittwieser C. Ionita
- Isliker H.
- Jacquier R.
- Jardin A.
- Kappatou A.
- Karpushov A.
- Kazantzidis P.-V.
- Keeling D.
- Kirneva N.
- Komm M.
- Kong M.
- Kovacic J.
- Krawczyk N.
- Kudlacek O.
- Kurki-Suonio T.
- Kwiatkowski R.
- Labit B.
- Lazzaro E.
- Linehan B.
- Lipschultz B.
- Llobet X.
- Lombroni R.
- Loschiavo V.P.
- Lunt T.
- Macusova E.
- Madsen J.
- Maljaars E.
- Mantica P.
- Maraschek M.
- Marchetto C.
- Marco A.
- Mariani A.
- Marini C.
- Martin Y.
- Matos F.
- Maurizio R.
- Mavkov B.
- Mazon D.
- Mccarthy P.
- Mcdermott R.
- Menkovski V.
- Merle A.
- Meyer H.
- Micheletti D.
- Militello F.
- Mitosinkova K.
- Mlynář J.
- Moiseenko V.
- Cabrera P.A. Molina
- Morales J.
- Moret J.-M.
- Moro A.
- Mumgaard R.T.
- Naulin V.
- Nem R.D.
- Nespoli F.
- Nielsen A.H.
- Nielsen S.K.
- Nocente M.
- Nowak S.
- Offeddu N.
- Orsitto F.P.
- Paccagnella R.
- Palha A.
- Papp G.
- Pau A.
- Pavlichenko R.O.
- Perek A.
- Ridolfini V. Pericoli
- Pesamosca F.
- Piergotti V.
- Pigatto L.
- Piovesan P.
- Piron C.
- Plyusnin V.
- Poli E.
- Porte L.
- Pucella G.
- Puiatti M.E.
- Pütterich T.
- Rabinski M.
- Rasmussen J. Juul
- Ravensbergen T.
- Reich M.
- Reimerdes H.
- Reimold F.
- Reux C.
- Ricci D.
- Ricci P.
- Rispoli N.
- Rosato J.
- Saarelma S.
- Salewski M.
- Salmi A.
- Sauter O.
- Scheffer M.
- Schlatter Ch.
- Schneider B.S.
- Schrittwieser R.
- Sharapov S.
- Sheeba R.R.
- Sheikh U.
- Shousha R.
- Silva M.
- Sinha J.
- Sozzi C.
- Spolaore M.
- Stipani L.
- Strand P.
- Tala T.
- Tema Biwole A.S.
- Teplukhina A.A.
- Testa D.
- Theiler C.
- Thornton A.
- Tomaž G.
- Tomes M.
- Tran M.Q.
- Tsironis C.
- Tsui C.K.
- Urban Joanna M
- Valisa M.
- Valla M.
- Vugt D. Van
- Vartanian S.
- Vasilovici O.
- Verhaegh K.
- Vermare L.
- Vianello N.
- Viezzer E.
- Vijvers W.A.J.
- Villone F.
- Voitsekhovitch I.
- Vu N.M.T.
- Walkden N.
- Wauters T.
- Weiland M.
- Weisen H.
- Wensing M.
- Wiesenberger M.
- Wilkie G.
- Wischmeier M.
- Wu K.
- Yoshida M.
- Zagorski R.
- Zanca P.
- Zebrowski J.
- Zisis A.
- Zuin M.
- Eurofusion Mst1 Team The
Nuclear Fusion, IOP Publishing, 2019, 59 (11), pp.112023. The research program of the TCV tokamak ranges from conventional to advanced-tokamak scenarios and alternative divertor configurations, to exploratory plasmas driven by theoretical insight, exploiting the device’s unique shaping capabilities. Disruption avoidance by real-time locked mode prevention or unlocking with electron-cyclotron resonance heating (ECRH) was thoroughly documented, using magnetic and radiation triggers. Runaway generation with high-Z noble-gas injection and runaway dissipation by subsequent Ne or Ar injection were studied for model validation. The new 1 MW neutral beam injector has expanded the parameter range, now encompassing ELMy H-modes in an ITER-like shape and nearly non-inductive H-mode discharges sustained by electron cyclotron and neutral beam current drive. In the H-mode, the pedestal pressure increases modestly with nitrogen seeding while fueling moves the density pedestal outwards, but the plasma stored energy is largely uncorrelated to either seeding or fueling. High fueling at high triangularity is key to accessing the attractive small edge-localized mode (type-II) regime. Turbulence is reduced in the core at negative triangularity, consistent with increased confinement and in accord with global gyrokinetic simulations. The geodesic acoustic mode, possibly coupled with avalanche events, has been linked with particle flow to the wall in diverted plasmas. Detachment, scrape-off layer transport, and turbulence were studied in L- and H-modes in both standard and alternative configurations (snowflake, super-X, and beyond). The detachment process is caused by power ‘starvation’ reducing the ionization source, with volume recombination playing only a minor role. Partial detachment in the H-mode is obtained with impurity seeding and has shown little dependence on flux expansion in standard single-null geometry. In the attached L-mode phase, increasing the outer connection length reduces the in–out heat-flow asymmetry. A doublet plasma, featuring an internal X-point, was achieved successfully, and a transport barrier was observed in the mantle just outside the internal separatrix. In the near future variable-configuration baffles and possibly divertor pumping will be introduced to investigate the effect of divertor closure on exhaust and performance, and 3.5 MW ECRH and 1 MW neutral beam injection heating will be added. (10.1088/1741-4326/ab25cb)
DOI : 10.1088/1741-4326/ab25cb
Cavity-enhanced photodetachment of H$^-$as a means to produce energetic neutral beams for phasma Heating
- Blondel Christophe
- Bresteau David
- Drag Cyril
Atoms, MDPI, 2019, 7 (1), pp.32. Neutral beam injection, for plasma heating, will supposedly be achieved, in ITER, by collisional detachment of a pre-accelerated D− beam. Collisional detachment, however, makes use of a D2-filled neutralisation chamber, which has severe drawbacks, including the necessity to set the D− -ion source at −1 MV. Photodetachment, in contradistinction, would have several advantages as a neutralisation method, including the absence of gas injection, and the possibility to set the ion source close to the earth potential. Photodetachment, however, requires a very high laser flux. The presented work has consisted in implementing an optical cavity, with a finesse greater than 3000, to make such a high illumination possible with a state-of-the-art CW (continuous-wave) laser. A 1.2 keV 1H− -beam (only 20 times slower than the 1 MeV 2D− ion beams to be prepared for ITER) was photodetached with more-than-50% efficiency, with only 24 W of CW laser input. This experimental demonstration paves the way for developing real-size photoneutralizers, based on the implementation of refolded optical cavities around the ion beams of neutral beam injectors. Depending on whether the specifications of the laser power or the cavity finesse will be more difficult to achieve in real scale, different architectures can be considered, with greater or smaller numbers of optical refoldings or (inclusively) optical cavities in succession, on the beam to be neutralised. (10.3390/atoms7010032)
DOI : 10.3390/atoms7010032
Plasma-surface interaction: dielectric and metallic targets and their influence on the electric field profile in a kHz AC-driven He plasma jet
- Sobota Ana
- Guaitella Olivier
- Sretenović G. B.
- Kovačević V. V.
- Slikboer Elmar
- Krstić I. B.
- Obradović B. M.
- Kuraica M. M.
Plasma Sources Science and Technology, IOP Publishing, 2019, 28 (4), pp.045003. Plasma catalysis, biomedical applications or atomic layer deposition at atmospheric pressure all make use of non-thermal plasmas in contact with a wide variety of surfaces. As the presence of a target (substrate) has been shown to modify the plasma in addition to the plasma modifying the target, it is reasonable to describe and study the plasma-surface as one system. This work shows how the presence of dielectric and metallic targets influences a kHz AC-driven discharge in a He plasma jet. Next to bringing the absolute values of the axial electric field along the plume of the jet, the presence of the surface has been shown to significantly elongate both the plume and the electric field profile. In addition, when a dielectric target is placed closer than the maximum length of the freely expanding jet, the electric field profile is enhanced only in the vicinity of the dielectric, typically between 0.3 and 2 mm above the target surface. The maximum measured relative increase is 31%, for 1000 SCCM flow with the target at 7 mm distance, when the electric field increased from 14.1 kV cm−1 for the freely expanding jet to 32.6 kV cm−1 when the jet was impinging on glass. Finally, a grounded metallic target enhances the electric field compared to the glass target only within a very thin layer just above the surface, typically about 0.2 mm. The highest measured electric field was 40.1 kV cm−1 at a grounded metallic target 12 mm away from the nozzle, for 1000 SCCM of helium flow. The discussion on the effects of the flow on the electric field profile are supported by the visualization of the flow. The discussion brings, among other, the comparison of properties between the 30 kHz AC-driven system and the 5 kHz pulsed jet. (10.1088/1361-6595/ab0c6a)
DOI : 10.1088/1361-6595/ab0c6a
Crossing of Plasma Structures by spacecraft: a path calculator
- Manuzzo Roberto
- Belmont Gérard
- Rezeau Laurence
- Califano F.
- Denton R E
Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2019, 124 (12), pp.10119-10140. When spacecraft (s/c) missions probe plasma structures (PSs) the relative location of the s/c with respect to the PS is unknown. This information is, however, needed to measure the geometrical features of the PS (orientation and thickness) and to understand the physical processes underlying the PS dynamics. Methods to determine the s/c location exist, but they need strong assumptions to be satisfied (stationarity and special spatial dependencies). The number of cases for which these assumptions are likely to be valid for the entire PS seems to be limited, and even weak departures from these hypotheses may affect the results. For a quasi‐1‐D geometry in particular, the determination of the velocity component along the two quasi‐invariant directions is very inaccurate and the assumption of strict stationarity may lead these quantities to diverge. In this paper we present new methods to compute the s/c trajectory through a PS, without a priori assumption on its spatial geometry, and able to work even in the presence of weak nonstationarities. The methods are tested both on artificial and real data, the latter provided by the Magnetospheric Multiscale mission probing the Earth's magnetopause. The 1‐D and 2‐D trajectories of the Magnetospheric Multiscale are found that can be used as an initial step for future reconstruction studies. Advanced minimization procedures to optimize the results are discussed. (10.1029/2019JA026632)
DOI : 10.1029/2019JA026632
Experimental and numerical investigation of the transient charging of a dielectric surface exposed to a plasma jet
- Slikboer Elmar
- Viegas Pedro
- Bonaventura Z.
- Garcia-Caurel Enric
- Sobota Ana
- Bourdon Anne
- Guaitella Olivier
Plasma Sources Science and Technology, IOP Publishing, 2019, 28 (9), pp.095016. This work investigates the dynamical charging of a surface under exposure of a non-equilibrium plasma jet at atmospheric pressure through a quantitative comparison between modeling and experiments. We show using mono-polar pulses with variable pulse duration and amplitude that the charging time (i.e. the time from impact of the ionization wave till the fall of the high voltage pulse) is a crucial element determining the plasma-surface interaction. This is done through direct measurements of the electric field induced inside the target using the optical diagnostic technique called Mueller polarimetry and comparison with the electric field calculated using a 2D fluid model of the plasma jet interaction with the target in the same conditions as in the experiments. When the charging time is kept relatively short (less than 100 ns), the surface spreading of the discharge and consequent surface charge deposition are limited. When it is relatively long (up to microseconds), the increased surface spreading and charge deposition significantly change the electric field to which the target is exposed during the charging time and when the applied voltage returns to zero. (10.1088/1361-6595/ab3c27)
DOI : 10.1088/1361-6595/ab3c27
Training on GNSS and Space Weather in Africa in the framework of the North-South scientific network GIRGEA
- Amory-Mazaudier Christine
- Fleury Rolland
- Masson F.
- Gadimova S.
- Anas Emran
Sun and Geosphere, BBC SWS Regional Network, 2019, 1 (141), pp.71-79. This paper presents the successful setting up of a research and teaching network for space weather in developed and fragile countries. This development took nearly a quarter of a century with the help of international cooperation. Numerous studies have been developed in different domains of Space Weather concerning the impact of solar events on the ionosphere and the Earth's magnetic field, ionospheric electric currents and the induced currents in the ground (GIC) Other studies have also been conducted on climate change, lightning and the movement of tectonic plates. We underline the importance of Global Navigation Satellite Systems [GNSS] for the development of space weather research and capacity building during the last decades (10.31401/SunGeo.2019.01.10)
DOI : 10.31401/SunGeo.2019.01.10
Energy Conversion and Electron Acceleration in the Magnetopause Reconnection Diffusion Region
- Pritchard K. R.
- Burch J. L.
- Fuselier S. A.
- Webster J. M.
- Torbert R. B.
- Argall M. R.
- Broll J.
- Genestreti K. J.
- Giles B. L.
- Le Contel Olivier
- Mukherjee J.
- Phan T. D.
- Rager A. C.
- Russell C. T.
- Strangeway R. J.
Geophysical Research Letters, American Geophysical Union, 2019, 46 (17-18), pp.10274-10282. Data are analyzed from a Magnetospheric Multiscale encounter with a dayside magnetopause reconnection region on 29 December 2016. The uniqueness of the event stems from the small ( 7 km) average spacecraft separation and the sequential sampling of an electron diffusion region with electron crescent distributions. We quantitatively investigate the earthward acceleration of magnetosheath electrons through the in-plane null by the polarization electric field EN that points radially outward from the magnetopause. The results compare favorably with previous plasma simulations with one important difference that the reconnection electric field (EM) extends throughout the region of strong EN so that both fields energize electrons in the same region. This acceleration is quantified here for the first time. As the spacecraft penetrate deeper into the region of enhanced EN, the magnetic reflection of lower-energy electrons produces a thinner crescent. (10.1029/2019GL084636)
DOI : 10.1029/2019GL084636
Non-thermal DBD plasma array on seed germination of different plant species
- Liu Bo
- Honnorat Bruno
- Yang Hang
- Arancibia Monreal J.
- Rajjou Loic
- Rousseau Antoine
Journal of Physics D: Applied Physics, IOP Publishing, 2019, 52 (2), pp.025401. A dielectric barrier discharge (DBD) reactor producing cold plasma at atmospheric pressure has been used to treat seeds of eight different species and investigate their responses in term of germination. The device is made of nine cylindrical DBDs organized in a array and partially immersed in water. O2, N2, and air were flown in the device; the cold plasma from such gas is formed in the bubbles and touch liquid surface. Seeds were either located inside the water during plasma treatment process (direct treatment) or were watered by the water exposed to cold plasma beforehand (indirect treatment). Such plasma activated water contains reactive oxygen species and reactive nitrogen species. The statistical analysis shows that the probability of germinating of treated mung bean, mustard and radish is significantly higher than in control groups (p  <  0.05) for indirect treatments. A comparison of different treatment modalities (direct versus indirect treatment and gas composition) on germination boost has been completed on mung bean seeds. It is shown that direct plasma treatment using different gas (O2, N2, and air) give a strong enhancement of the mung bean germination probability compared to the control group; in the case of indirect treatment, only plasma air-treated water lead to a significant germination boost compared to the control group; this effect is still smaller than the one obtained using a direct treatment. (10.1088/1361-6463/aae771)
DOI : 10.1088/1361-6463/aae771
Dependence on plasma shape and plasma fueling for small edge-localized mode regimes in TCV and ASDEX Upgrade
- Labit B.
- Eich T.
- Harrer G.F.
- Wolfrum E.
- Bernert M.
- Dunne M.G.
- Frassinetti L.
- Hennequin Pascale
- Maurizio R.
- Merle A.
- Meyer H.
- Saarelma S.
- Sheikh U.
- Eurofusion Mst1 Team The
Nuclear Fusion, IOP Publishing, 2019, 59 (8), pp.086020. Within the EUROfusion MST1 work package, a series of experiments has been conducted on AUG and TCV devices to disentangle the role of plasma fueling and plasma shape for the onset of small ELM regimes. On both devices, small ELM regimes with high confinement are achieved if and only if two conditions are fulfilled at the same time. Firstly, the plasma density at the separatrix must be large enough (), leading to a pressure profile flattening at the separatrix, which stabilizes type-I ELMs. Secondly, the magnetic configuration has to be close to a double null (DN), leading to a reduction of the magnetic shear in the extreme vicinity of the separatrix. As a consequence, its stabilizing effect on ballooning modes is weakened. (10.1088/1741-4326/ab2211)
DOI : 10.1088/1741-4326/ab2211
Inverse cascade of hybrid helicity in BΩ-MHD turbulence
- Menu Mélissa
- Galtier Sébastien
- Petitdemange Ludovic
Physical Review Fluids, American Physical Society, 2019, 4, pp.073701. We investigate the impact of a solid-body rotation Ω0 on the large-scale dynamics of an incompressible magnetohydrodynamic turbulent flow in presence of a background magnetic field B0 and at low Rossby number. Three-dimensional direct numerical simulations are performed in a periodic box, at unit magnetic Prandtl number and with a forcing at intermediate wave number kf=20. When Ω0 is aligned with B0 (i.e., θ≡(Ω0,B0)=0), inverse transfer is found for the magnetic spectrum at k<kf. This transfer is stronger when the forcing excites preferentially right-handed (rather than left-handed) fluctuations; it is smaller when θ>0 and becomes weak when θ≥35∘. These properties are understood as the consequence of an inverse cascade of hybrid helicity which is an inviscid/ideal invariant of this system when θ=0. Hybrid helicity emerges, therefore, as a key element for understanding rotating dynamos. Implication of these findings on the origin of the alignment of the magnetic dipole with the rotation axis in planets and stars is discussed. (10.1103/PhysRevFluids.4.073701)
DOI : 10.1103/PhysRevFluids.4.073701
Comparison between ad-hoc and instability-induced electron anomalous transport in a 1D fluid simulation of Hall-effect thruster
- Martorelli Roberto
- Lafleur Trevor
- Bourdon Anne
- Chabert Pascal
Physics of Plasmas, American Institute of Physics, 2019, 26 (8), pp.083502. Anomalous electron transport is a long-standing problem in the understanding of Hall-effect thrusters. Recent results have suggested as a possible cause a kinetic instability, but few attempts have succeeded in implementing such phenomena in a fluid simulation of the thruster. The common approach in this case relies on including an ad-hoc model of the anomalous transport and so to fit experimental results. We propose here a comparison between the friction force and the anomalous heating arising from the ad-hoc model, with the corresponding effects coming from the use of the instability-induced transport. The results are obtained through a one-dimensional fluid simulation of the Hall-effect thruster with ad-hoc anomalous transport. The comparison shows good agreement between the two approaches, suggesting indeed that the instability-induced anomalous transport is the good candidate for reproducing the ad-hoc simulations and paving the way for a full self-consistent implementation of the phenomena in a fluid simulation. (10.1063/1.5089008)
DOI : 10.1063/1.5089008
ViDA: a Vlasov-DArwin solver for plasma physics at electron scales
- Pezzi Oreste
- Cozzani Giulia
- Califano Francesco
- Valentini Francesco
- Guarrasi Massimiliano
- Camporeale Enrico
- Brunetti Gianfranco
- Retinò Alessandro
- Veltri Pierluigi
Journal of Plasma Physics, Cambridge University Press (CUP), 2019, 85 (5), pp.905850506. We present a VlasovDArwin numerical code (ViDA) specifically designed to address plasma physics problems, where small-scale high accuracy is requested even during the nonlinear regime to guarantee a clean description of the plasma dynamics at fine spatial scales. The algorithm provides a low-noise description of proton and electron kinetic dynamics, by splitting in time the multi-advection Vlasov equation in phase space. Maxwell equations for the electric and magnetic fields are reorganized according to the Darwin approximation to remove light waves. Several numerical tests show that ViDA successfully reproduces the propagation of linear and nonlinear waves and captures the physics of magnetic reconnection. We also discuss preliminary tests of the parallelization algorithm efficiency, performed at CINECA on the Marconi-KNL cluster. ViDA will allow the running of Eulerian simulations of a non-relativistic fully kinetic collisionless plasma and it is expected to provide relevant insights into important problems of plasma astrophysics such as, for instance, the development of the turbulent cascade at electron scales and the structure and dynamics of electron-scale magnetic reconnection, such as the electron diffusion region. (10.1017/S0022377819000631)
DOI : 10.1017/S0022377819000631
Plasma gun for medical applications: engineering an equivalent electrical target of human body and deciphering relevant electrical parameters
- Judée Florian
- Dufour Thierry
Journal of Physics D: Applied Physics, IOP Publishing, 2019, 52 (16), pp.16 - 18. Simulations and experimental works have been carried out in a complementary way to engineer a basic material target mimicking the same dielectric properties of the human body. It includes a resistor in parallel with a capacitor, whose values (Rh=1500 Ω and Ch=100 pF) are estimated in regard of parameters commonly utilized upon in vivo campaigns (frequency=30 kHz, gap=10 mm, high voltage electrode surface=12.6 mm 2). This equivalent electrical human body (EEHB) circuit can be used as a reference and realistic target to calibrate electrical properties of therapeutic plasma sources before their utilization on patients. In this letter, we consider a configuration where this EEHB target interacts with a plasma gun (PG). Plasma power measurements performed in such configuration clearly indicate two operating modes depending on the value of the supplied voltage. Hence, the plasma gun generates pulsed atmospheric plasma streams likely to present therapeutic interest for voltages comprised between 3.0 and 8.5 kV while for higher values, transient arcs of thermal plasma are generated and represent substantial risks for the patient. (10.1088/1361-6463/ab03b8)
DOI : 10.1088/1361-6463/ab03b8
Experimental demonstration of multifrequency impedance matching for tailored voltage waveform plasmas
- Wang Junkang
- Diné Sébastien
- Booth Jean-Paul
- Johnson Erik
Journal of Vacuum Science & Technology A, American Vacuum Society, 2019, 37 (2), pp.021303. Driving radiofrequency capacitively coupled plasmas by multiharmonic tailored voltage waveforms (TVWs) has been shown to allow considerable control over various plasma properties for surface processing applications. However, industrial adoption of this technology would benefit from more efficient solutions to the challenge of impedance matching the radiofrequency power source to the load simultaneously at multiple harmonic frequencies. The authors report on the design and demonstration of a simple, practical multifrequency matchbox (MFMB) based on a network of LC resonant circuits. The performance of the matchbox was quantified in terms of a range of matchable impedances (when matching a single frequency at a time), as well as for the independence of each match to changes at adjacent harmonics. The effectiveness of the MFMB was demonstrated experimentally on an Ar plasma excited by a three-frequency TVW with a fundamental frequency of 13.56 MHz. Under the plasma conditions studied, the power coupling efficiency (at the generator output) was increased from less than 40% (without impedance matching) to between 80% and 99% for the different exciting frequencies. (10.1116/1.5056205)
DOI : 10.1116/1.5056205
[Plasma 2020 Decadal] Disentangling the Spatiotemporal Structure of Turbulence Using Multi-Spacecraft Data
- Tenbarge J.
- Alexandrova O.
- Boldyrev S.
- Califano F.
- Cerri S.
- Chen C.
- Howes G.
- Horbury T.
- Isenberg P.
- Ji H.
- Klein K.
- Krafft C.
- Kunz M.
- Loureiro N.
- Mallet A.
- Maruca B.
- Matthaeus W.
- Meyrand R.
- Quataert E.
- Perez J.
- Roberts O.
- Sahraoui F.
- Salem C.
- Schekochihin A.
- Spence H.
- Squire J.
- Told D.
- Verscharen D.
- Wicks R.
Plasma 2020 Decadal Survey, 2019. This white paper submitted for 2020 Decadal Assessment of Plasma Science concerns the importance of multi-spacecraft missions to address fundamental questions concerning plasma turbulence. Plasma turbulence is ubiquitous in the universe, and it is responsible for the transport of mass, momentum, and energy in such diverse systems as the solar corona and wind, accretion discs, planet formation, and laboratory fusion devices. Turbulence is an inherently multi-scale and multi-process phenomenon, coupling the largest scales of a system to sub-electron scales via a cascade of energy, while simultaneously generating reconnecting current layers, shocks, and a myriad of instabilities and waves. The solar wind is humankind's best resource for studying the naturally occurring turbulent plasmas that permeate the universe. Since launching our first major scientific spacecraft mission, Explorer 1, in 1958, we have made significant progress characterizing solar wind turbulence. Yet, due to the severe limitations imposed by single point measurements, we are unable to characterize sufficiently the spatial and temporal properties of the solar wind, leaving many fundamental questions about plasma turbulence unanswered. Therefore, the time has now come wherein making significant additional progress to determine the dynamical nature of solar wind turbulence requires multi-spacecraft missions spanning a wide range of scales simultaneously. A dedicated multi-spacecraft mission concurrently covering a wide range of scales in the solar wind would not only allow us to directly determine the spatial and temporal structure of plasma turbulence, but it would also mitigate the limitations that current multi-spacecraft missions face, such as non-ideal orbits for observing solar wind turbulence. Some of the fundamentally important questions that can only be addressed by in situ multipoint measurements are discussed. (10.48550/arXiv.1903.05710)
DOI : 10.48550/arXiv.1903.05710
Electron Diffusion Regions in Magnetotail Reconnection Under Varying Guide Fields
- Chen L.-J
- Wang S.
- Hesse M.
- Ergun R.
- Moore T.
- Giles B.
- Bessho N.
- Russell C.
- Burch J.
- Torbert R. B
- Genestreti K. J
- Paterson W.
- Pollock C.
- Lavraud B.
- Le Contel Olivier
- Strangeway R.
- Khotyaintsev Yu V
- Lindqvist P.-A
Geophysical Research Letters, American Geophysical Union, 2019, 46 (12), pp.6230-6238. Kinetic structures of electron diffusion regions (EDRs) under finite guide fields in magnetotail reconnection are reported. The EDRs with guide fields 0.14–0.5 (in unit of the reconnecting component) are detected by the Magnetospheric Multiscale spacecraft. The key new features include the following: (1) cold inflowing electrons accelerated along the guide field and demagnetized at the magnetic field minimum while remaining a coherent population with a low perpendicular temperature, (2) wave fluctuations generating strong perpendicular electron flows followed by alternating parallel flows inside the reconnecting current sheet under an intermediate guide field, and (3) gyrophase bunched electrons with high parallel speeds leaving the X‐line region. The normalized reconnection rates for the three EDRs range from 0.05 to 0.3. The measurements reveal that finite guide fields introduce new mechanisms to break the electron frozen‐in condition. (10.1029/2019GL082393)
DOI : 10.1029/2019GL082393
MMS Observations of Kinetic-size Magnetic Holes in the Terrestrial Magnetotail Plasma Sheet
- Huang S. Y.
- He L. H.
- Yuan Z. G.
- Sahraoui Fouad
- Le Contel Olivier
- Deng X. H.
- Zhou M.
- Fu H.S.
- Jiang K.
- Yu X. D.
- Li H. M.
- Deng D.
- Pollock C. J.
- Torbert R. B.
- Burch J. L.
The Astrophysical Journal, American Astronomical Society, 2019, 875 (2), pp.113, 8 pp. Kinetic-size magnetic holes (KSMHs) in the terrestrial magnetotail plasma sheet are statistically investigated using the observations from the Magnetospheric Multiscale mission. The scales of KSMHs are found to be smaller than one ion gyroradius or tens of electron gyroradii. The occurrence distributions of KSMHs have dawn−dusk asymmetry (duskside preference) in the magnetotail, which may be caused by the Hall effect. Most events of KSMHs (71.7%) are accompanied by a substorm, implying that substorms may provide favorable conditions for the excitation of KSMHs. However, there is a weak correlation between KSMHs and magnetic reconnection. The statistical results reveal that for most of the events, the electron total temperature and perpendicular temperature increase while the electron parallel temperature decreases inside the KSMHs. The electron temperature anisotropy (T e⊥/Te| | > 1) is observed in 72% of KSMHs. Whistler-mode waves are frequently observed inside the KSMHs, and most (92%) KSMHs associated with whistler waves have enhancements of electron perpendicular distributions and satisfy the unstable condition of whistler instability. This suggests that the observed electron-scale whistler waves, locally generated by the electron temperature anisotropy, could couple with the electron-scale KSMHs. The observed features of KSMHs and their coupling to electron-scale whistlers are similar to the ones in the turbulent magnetosheath, implying that they are ubiquitous in the space plasmas. The generation of KSMHs in the plasma sheet could be explained by an electron vortex magnetic hole, magnetosonic solitons, and/or ballooning/interchange instabilities. (10.3847/1538-4357/ab0f2f)
DOI : 10.3847/1538-4357/ab0f2f
The Space Physics Environment Data Analysis System (SPEDAS)
- Angelopoulos V.
- Cruce P.
- Drozdov A.
- Grimes E. W.
- Hatzigeorgiu N.
- King D. A.
- Larson D. E.
- Lewis J. W.
- Mctiernan J. M.
- Roberts D. A.
- Russell C. L.
- Hori T.
- Kasahara Y.
- Kumamoto A.
- Matsuoka A.
- Miyashita Y.
- Miyoshi Y.
- Shinohara I.
- Teramoto M.
- Faden J. B.
- Halford A. J.
- Mccarthy M.
- Millan R. M.
- Sample J. G.
- Smith D. M.
- Woodger L. A.
- Masson A.
- Narock A. A.
- Asamura K.
- Chang T. F.
- Chiang C.-Y.
- Kazama Y.
- Keika K.
- Matsuda S.
- Segawa T.
- Seki K.
- Shoji M.
- Tam S. W. Y.
- Umemura N.
- Wang B.-J.
- Wang S.-Y.
- Redmon R.
- Rodriguez J. V.
- Singer H. J.
- Vandegriff J.
- Abe S.
- Nose M.
- Shinbori A.
- Tanaka Y.-M.
- Ueno S.
- Andersson L.
- Dunn P.
- Fowler C.
- Halekas J. S.
- Hara T.
- Harada Y.
- Lee C. O.
- Lillis R.
- Mitchell D. L.
- Argall M. R.
- Bromund K.
- Burch J. L.
- Cohen I. J.
- Galloy M.
- Giles B. L.
- Jaynes A. N.
- Le Contel Olivier
- Oka M.
- Phan T. D.
- Walsh B. M.
- Westlake J.
- Wilder F. D.
- Bale S. D.
- Livi R.
- Pulupa M.
- Whittlesey P.
- Dewolfe A.
- Harter B.
- Lucas E.
- Auster U.
- Bonnell J. W.
- Cully C. M.
- Donovan E.
- Ergun R. E.
- Frey H. U.
- Jackel B.
- Keiling A.
- Korth H.
- Mcfadden J. P.
- Nishimura Y.
- Plaschke F.
- Robert Patrick
- Turner D. L.
- Weygand J. M.
- Candey R. M.
- Johnson R. C.
- Kovalick T.
- Liu M. H.
- Mcguire R. E.
- Breneman A.
- Kersten K.
- Schroeder P.
Space Science Reviews, Springer Verlag, 2019, 215, pp.9, 46p. With the advent of the Heliophysics/Geospace System Observatory (H/GSO), a complement of multi-spacecraft missions and ground-based observatories to study the space environment, data retrieval, analysis, and visualization of space physics data can be daunting. The Space Physics Environment Data Analysis System (SPEDAS), a grass-roots software development platform (<ExternalRef> <RefSource>www.spedas.org</RefSource> <RefTarget Address="http://www.spedas.org" TargetType="URL"/> </ExternalRef>), is now officially supported by NASA Heliophysics as part of its data environment infrastructure. It serves more than a dozen space missions and ground observatories and can integrate the full complement of past and upcoming space physics missions with minimal resources, following clear, simple, and well-proven guidelines. Free, modular and configurable to the needs of individual missions, it works in both command-line (ideal for experienced users) and Graphical User Interface (GUI) mode (reducing the learning curve for first-time users). Both options have "crib-sheets," user-command sequences in ASCII format that can facilitate record-and-repeat actions, especially for complex operations and plotting. Crib-sheets enhance scientific interactions, as users can move rapidly and accurately from exchanges of technical information on data processing to efficient discussions regarding data interpretation and science. SPEDAS can readily query and ingest all International Solar Terrestrial Physics (ISTP)-compatible products from the Space Physics Data Facility (SPDF), enabling access to a vast collection of historic and current mission data. The planned incorporation of Heliophysics Application Programmer's Interface (HAPI) standards will facilitate data ingestion from distributed datasets that adhere to these standards. Although SPEDAS is currently Interactive Data Language (IDL)-based (and interfaces to Java-based tools such as Autoplot), efforts are under-way to expand it further to work with python (first as an interface tool and potentially even receiving an under-the-hood replacement). We review the SPEDAS development history, goals, and current implementation. We explain its "modes of use" with examples geared for users and outline its technical implementation and requirements with software developers in mind. We also describe SPEDAS personnel and software management, interfaces with other organizations, resources and support structure available to the community, and future development plans. (10.1007/s11214-018-0576-4)
DOI : 10.1007/s11214-018-0576-4
Properties of the Turbulence Associated with Electron-only Magnetic Reconnection in Earth's Magnetosheath
- Stawarz J. E.
- Eastwood Jonathan P.
- Phan T. D.
- Gingell I. L.
- Shay M. A.
- Burch J. L.
- Ergun R. E.
- Giles B. L.
- Gershman D. J.
- Le Contel Olivier
- Lindqvist P.-A.
- Russell C. T.
- Strangeway R. J.
- Torbert R. B.
- Argall M. R.
- Fischer D.
- Magnes W.
- Franci L.
The Astrophysical Journal Letters, Bristol : IOP Publishing, 2019, 877 (2), pp.L37. Turbulent plasmas generate intense current structures, which have long been suggested as magnetic reconnection sites. Recent Magnetospheric Multiscale observations in Earth's magnetosheath revealed a novel form of reconnection where the dynamics only couple to electrons, without ion involvement. It was suggested that such dynamics were driven by magnetosheath turbulence. In this study, the fluctuations are examined to determine the properties of the turbulence and if a signature of reconnection is present in the turbulence statistics. The study reveals statistical properties consistent with plasma turbulence with a correlation length of ~10 ion inertial lengths. When reconnection is more prevalent, a steepening of the magnetic spectrum occurs at the length scale of the reconnecting current sheets. The statistics of intense currents suggest the prevalence of electron-scale current sheets favorable for electron reconnection. The results support the hypothesis that electron reconnection is driven by turbulence and highlight diagnostics that may provide insight into reconnection in other turbulent plasmas. (10.3847/2041-8213/ab21c8)
DOI : 10.3847/2041-8213/ab21c8
Signatures of Cold Ions in a Kinetic Simulation of the Reconnecting Magnetopause
- Dargent Jérémy
- Aunai Nicolas
- Lavraud B.
- Toledo-Redondo Sergio
- Califano F.
Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2019, 124 (4), pp.2497-2514. Abstract At the Earth's magnetopause, a low-energy ion population of ionospheric origin is commonly observed at the magnetospheric side. In this work we use a 2-D fully kinetic simulation to identify several original signatures related to the dynamics of cold ions involved in magnetic reconnection at the asymmetric dayside magnetopause. We identify several original signatures of the cold ions dynamics driven by the development of magnetic reconnection at the asymmetric dayside magnetopause. We find that cold ions tend to rarefy in the diffusion region, while their density is enhanced as a result of compression along magnetospheric separatrices. We also observe the formation of crescent-shaped cold ion distribution functions along the separatrices in the near-exhaust region, and we present an analytical model to explain this signature. Finally, we give evidence of a localized parallel heating of cold ions. These signatures should be detected with the magnetospheric multiscale mission high-resolution observations. (10.1029/2018JA026343)
DOI : 10.1029/2018JA026343
High-Resolution Measurements of the Cross-Shock Potential, Ion Reflection, and Electron Heating at an Interplanetary Shock by MMS
- Cohen Ian J.
- Schwartz Steven J.
- Goodrich Katherine A.
- Ahmadi Narges
- Ergun Robert E.
- Fuselier Stephen A.
- Desai Mihir I.
- Christian Eric R.
- Mccomas David J.
- Zank Gary P.
- Shuster Jason R.
- Vines Sarah K.
- Mauk Barry H.
- Decker Robert B.
- Anderson Brian J.
- Westlake Joseph H.
- Le Contel Olivier
- Breuillard Hugo
- Giles Barbara L.
- Torbert Roy B.
- Burch James L.
Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2019, 124, pp.3961-3978. The Magnetospheric Multiscale (MMS) spacecraft obtained unprecedented high-time resolution multipoint particle and field measurements of an interplanetary shock event on 8 January 2018. The spacecraft encountered the supercritical forward shock of a forward/reverse shock pair in the pristine solar wind upstream of the bow shock near the subsolar point as they neared apogee at 25 RE. The high-time resolution measurements from the four spacecraft, separated by only 20 km, allowed direct measurement of particle distributions revealing evidence of electron heating and near specularly reflected ions. The cross-shock potential is calculated directly from 3-D electric field measurements. This is the first reported direct high temporal resolution (<1 s) observation at an interplanetary shock of near specularly reflected ions. Calculation of the cross-shock potential yields a potential jump significant enough to reflect at least some of the protons from the incident solar wind beam. The cross-shock potential calculated here is consistent with previous estimations based on particle measurements and numerical/analytical simulations. The ambipolar contribution to the cross-shock potential calculated from the four-spacecraft divergence of the electron pressure tensor is somewhat higher than that inferred form the Liouville-mapped electron energy gain across the shock. Furthermore, the high-time-resolution 3-D electric field measurements reported here reveal small-scale nonlinear structures embedded in the shock layer that contribute to the nonmonotonic shock transition. (10.1029/2018JA026197)
DOI : 10.1029/2018JA026197
[Plasma 2020 Decadal] Multipoint Measurements of the Solar Wind: A Proposed Advance for Studying Magnetized Turbulence of the Solar Wind: A Proposed Advance for Studying Magnetized Turbulence
- G. Klein Kristopher
- Alexandrova Olga
- Bookbinder Jay
- Caprioli D.
- W. Case A.
- D. G. Chandran B.
- J. Chen L.
- Horbury T.
- C. Kasper J.
- Le Contel Olivier
- A. Maruca B.
- Matthaeus W. H.
- Retinò Alessandro
- Roberts O.
- Schekochihin A.
- Skoug Ruth M.
- W. Smith C.
- Steinberg John T.
- Spence H. E.
- Vasquez B.
- M. Tenbarge J.
- Verscharen Daniel
- Whittlesey P.
- Jian L.
, 2019.
SOTE: A Nonlinear Method for Magnetic Topology Reconstruction in Space Plasmas
- Liu Y. Y.
- Fu H.S.
- Olshevsky V.
- Pontin D. I.
- Liu C. M.
- Wang Z.
- Chen G.
- Dai L.
- Retinò Alessandro
The Astrophysical Journal Supplement, American Astronomical Society, 2019, 244 (2), pp.31. Complex magnetic structures are ubiquitous in turbulent astrophysical plasmas. Such structures can be host to many dynamic processes, such as magnetic reconnection and energy dissipation. Thus, revealing the 3D topologies of these structures is necessary. In this study, we propose a new method to reconstruct complex magnetic topologies in quasi-steady space plasmas, by utilizing eight-point measurements of magnetic fields and particles. Such a method, based on the Second-Order Taylor Expansion (SOTE) of a magnetic field, is nonlinear; it is constrained by \rm∇ · \boldsymbolB=0 and \rm∇ × \boldsymbolB=μ _0\boldsymbolJ, where \boldsymbolJ=ne(\boldsymbolV_\boldsymboli-\boldsymbolV_\boldsymbole) is from particle moments. A benchmark test of this method, using the simulation data, shows that the method can give accurate reconstruction results within an area about three times the size of a spacecraft tetrahedron. By comparing to the previous First-Order Taylor Expansion (FOTE) method, this method (SOTE) gives similar results for reconstructing quasilinear structures but exhibits better accuracy in reconstructing nonlinear structures. Such a method will be useful to the multi-scale missions, such as the future European Space Agency's "cross-scale" mission and China's "self-adaptive" mission. Also, it can be applied to four-point missions, such as Cluster and the Magnetospheric Multiscale Mission. We demonstrated how to apply this method to the four-point missions. In principle, this method will be useful to study shocks, magnetic holes, dipolarization fronts, and other nonlinear structures in space plasmas (10.3847/1538-4365/ab391a)
DOI : 10.3847/1538-4365/ab391a
Collision risk prediction for constellation design
- Lucken Romain
- Giolito Damien
Acta Astronautica, Elsevier, 2019, 161, pp.492-501. INDEMN is an object-oriented program dedicated to the modeling of the evolution of the densities of space objects. Following the work achieved by D. Kessler (1978) and by other authors more recently (G. L. Somma, IAC 2016, A6-IP3; A. Rossi, DPPS 2004, 197), the dynamical model is based on a source and sink approach for various altitudes. The source terms represent the future launches, the explosion of intact spacecrafts, and the collision between objects. Different collision cross sections are used for the various types of objects and the number of debris generated is based on the NASA break-up model. The sink terms are the drag and the end-of-life de-orbitation for the satellites launched after 2009, with a controllable success rate. The code was validated against former simulations performed with statistical and semi-deterministic models. In addition to the classical object types featured in several statistical codes, which are intact objects, explosion debris, and collision debris, a new type representing the satellites of a specific constellation is included. These satellites orbit with altitudes close to 1200 km and they can perform collision avoidance maneuvers as long as they are fully operational. It is shown that, under realistic assumptions, if only one primary collision occurs at an altitude of 800 km, the probability of a collision involving a constellation satellite becomes larger than 2% by 2035, which highly jeopardizes the satellite constellation as a whole. (10.1016/j.actaastro.2019.04.003)
DOI : 10.1016/j.actaastro.2019.04.003
Correction to: Statistical Analysis of Solar Events Associated with Storm Sudden Commencements over One Year of Solar Maximum During Cycle 23: Propagation from the Sun to the Earth and Effects
- Bocchialini Karine
- Grison B.
- Menvielle Michel
- Chambodut Aude
- Cornilleau-Wehrlin Nicole
- Fontaine Dominique
- Marchaudon Aurélie
- Pick M.
- Pitout Frédéric
- Schmieder Brigitte
- Régnier S.
- Zouganelis I.
Solar Physics, Springer Verlag, 2019, 294, pp.art. 38. Taking the 32 storm sudden commencements (SSCs) listed by the International Service of Geomagnetic Indices (ISGI) of the Observatory de l’Ebre during 2002 (solar activity maximum in Cycle 23) as a starting point, we performed a multi-criterion analysis based on observations (propagation time, velocity comparisons, sense of the magnetic field rotation, radio waves) to associate them with solar sources, identified their effects in the interplanetary medium, and looked at the response of the terrestrial ionized and neutral environment. We find that 28 SSCs can be related to 44 coronal mass ejections (CMEs), 15 with a unique CME and 13 with a series of multiple CMEs, among which 19 (68%) involved halo CMEs. Twelve of the 19 fastest CMEs with speeds greater than 1000 km s−1 are halo CMEs. For the 44 CMEs, including 21 halo CMEs, the corresponding X-ray flare classes are: 4 X-class, 19 M-class, and 21 C-class flares. The probability for an SSC to occur is 75% if the CME is a halo CME. Among the 500, or even more, front-side, non-halo CMEs recorded in 2002, only 23 could be the source of an SSC, i.e. 5%. The complex interactions between two (or more) CMEs and the modification of their trajectories have been examined using joint white-light and multiple-wavelength radio observations. The detection of long-lasting type IV bursts observed at metric–hectometric wavelengths is a very useful criterion for the CME–SSC association. The events associated with the most depressed Dst values are also associated with type IV radio bursts. The four SSCs associated with a single shock at L1 correspond to four radio events exhibiting characteristics different from type IV radio bursts. The solar-wind structures at L1 after the 32 SSCs are 12 magnetic clouds (MCs), 6 interplanetary coronal mass ejections (ICMEs) without an MC structure, 4 miscellaneous structures, which cannot unambiguously be classified as ICMEs, 5 corotating or stream interaction regions (CIRs/SIRs), one CIR caused two SSCs, and 4 shock events; notethat one CIR caused two SSCs. The 11 MCs listed in 3 or more MC catalogs covering the year 2002 are associated with SSCs. For the three most intense geomagnetic storms (based on Dst minima) related to MCs, we note two sudden increases of the Dst, at the arrival of the sheath and the arrival of the MC itself. In terms of geoeffectiveness, the relation between the CME speed and the magnetic-storm intensity, as characterized using the Dst magnetic index, is very complex, but generally CMEs with velocities at the Sun larger than 1000 km s−1 have larger probabilities to trigger moderate or intense storms. The most geoeffective events are MCs, since 92% of them trigger moderate or intense storms, followed by ICMEs (33%). At best, CIRs/SIRs only cause weak storms. We show that these geoeffective events (ICMEs or MCs) trigger an increased and combined auroral kilometric radiation (AKR) and non-thermal continuum (NTC) wave activity in the magnetosphere, an enhanced convection in the ionosphere, and a stronger response in the thermosphere. However, this trend does not appear clearly in the coupling functions, which exhibit relatively weak correlations between the solar-wind energy input and the amplitude of various geomagnetic indices, whereas the role of the southward component of the solar-wind magnetic field is confirmed. Some saturation appears for Dst values <−100nT on the integrated values of the polar and auroral indices. (10.1007/s11207-019-1426-6)
DOI : 10.1007/s11207-019-1426-6

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