Publications

2018

• The effect of liquid target on a nonthermal plasma jet−imaging, electric fields, visualization of gas flow and optical emission spectroscopy
  
  • Kovačević Vv
  • Sretenović Gb
  • Slikboer Elmar
  • Guaitella Olivier
  • Sobota Ana
  • Kuraica Mm
  Journal of Physics D: Applied Physics, IOP Publishing, 2018, 51 (6), pp.065202. The article describes the complex study of the interaction of a helium plasma jet with distilled water and saline. The discharge development, spatial distribution of the excited species, electric field measurement results and the results of the Schlieren imaging are presented. The results of the experiments showed that the plasmaliquid interaction could be prolonged with the proper choice of the gas composition between the jet nozzle and the target. This depends on the gas flow and the target distance. Increased conductivity of the liquid does not affect the discharge properties significantly. An increase of the gas flow enables an extension of the plasma duration on the liquid surface up to 10 µs, but with a moderate electric field strength in the ionization wave. In contrast, there is a significant enhancement of the electric field on the liquid surface, up to 30 kV cm−1 for low flows, but with a shorter time of the overall plasma liquid interaction. Ignition of the plasma jet induces a gas flow modification and may cause turbulences in the gas flow. A significant influence of the plasma jet causing a mixing in the liquid is also recorded and it is found that the plasma jet ignition changes the direction of the liquid circulation. (10.1088/1361-6463/aaa288)
  DOI : 10.1088/1361-6463/aaa288
• On the origin of the energy dissipation anomaly in (Hall) magnetohydrodynamics
  
  • Galtier Sébastien
  Journal of Physics A: Mathematical and General (1975 - 2006), IOP Publishing, 2018, 51. Incompressible Hall magnetohydrodynamics (MHD) may be the subject of energy dissipation anomaly which stems from the lack of smoothness of the velocity and magnetic fields. I derive the exact expression of which appears to be closely connected with the well-known 4/3 exact law of Hall MHD turbulence theory. This remarkable similitude suggests a deeper mathematical property of the fluid equations. In the MHD limit, the expression of differs from the one derived by Gao et al (2013 Acta Math. Sci. 33 865−71) which presents miscalculations. The energy dissipation anomaly can be used to better estimate the local heating in space plasmas where in situ measurements are accessible. (10.1088/1751-8121/aabbb5)
  DOI : 10.1088/1751-8121/aabbb5
• Magnetospheric Multiscale Observations of an Ion Diffusion Region With Large Guide Field at the Magnetopause: Current System, Electron Heating, and Plasma Waves
  
  • Zhou M.
  • Berchem J.
  • Walker R. J.
  • El-Alaoui M.
  • Goldstein M. L.
  • Lapenta G.
  • Deng X.
  • Li J.
  • Le Contel Olivier
  • Graham D. B.
  • Lavraud B.
  • Paterson W. R.
  • Giles B. L.
  • Burch J. L.
  • Torbert R. B.
  • Russell C. T.
  • Strangeway R. J.
  • Zhao C.
  • Ergun R. E.
  • Lindqvist P.-A.
  • Marklund G.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2018, 123 (3), pp.1834-1852. We report Magnetospheric Multiscale (MMS) observations of a reconnecting current sheet in the presence of a weak density asymmetry with large guide field at the dayside magnetopause. An ion diffusion region (IDR) was detected associated with this current sheet. Parallel current dominated over the perpendicular current in the IDR, as found in previous studies of component reconnection. Electrons were preferentially heated parallel to the magnetic field within the IDR. The heating was manifested as a flattop distribution below 400eV. Two types of electromagnetic electron whistler waves were observed within the regions where electrons were heated. One type of whistler wave was associated with nonlinear structures in E-|| with amplitudes up to 20mV/m. The other type was not associated with any structures in E-||. Poynting fluxes of these two types of whistler waves were directed away from the X-line. We suggest that the nonlinear evolution of the oblique whistler waves gave rise to the solitary structures in E-||. There was a perpendicular super-Alfvenic outflow jet that was carried by magnetized electrons. Intense electrostatic lower hybrid drift waves were localized in the current sheet center and were probably driven by the super-Alfvenic electron jet, the velocity of which was approximately equal to the diamagnetic drift of demagnetized ions. Our observations suggest that the guide field significantly modified the structures (Hall electromagnetic fields and current system) and wave properties in the IDR. (10.1002/2017JA024517)
  DOI : 10.1002/2017JA024517
• Nested polyhedra model of isotropic magnetohydrodynamic turbulence
  
  • Gürcan Özgür D.
  Physical Review E, American Physical Society (APS), 2018, 97, pp.063111. A nested polyhedra model has been developed for magnetohydrodynamic turbulence. Driving only the velocity field at large scales with random, divergence-free forcing results in a clear, stationary k^-5/3 spectrum for both kinetic and magnetic energies. Since the model naturally effaces disparate scale interactions, does not have a guide field, and avoids injecting any sign of helicity by random forcing, the resulting three-dimensional k spectrum is statistically isotropic. The strengths and weaknesses of the model are demonstrated by considering large or small magnetic Prandtl numbers. It was also observed that the timescale for the equipartition offset with those of the smallest scales shows a k^-1/2 scaling. (10.1103/PhysRevE.97.063111)
  DOI : 10.1103/PhysRevE.97.063111
• Calculated electron impact dissociation cross sections for molecular chlorine (Cl 2 )
  
  • Hamilton James R.
  • Tennyson Jonathan
  • Booth Jean-Paul
  • Gans Timo
  • Gibson Andrew
  Plasma Sources Science and Technology, IOP Publishing, 2018, 27 (9), pp.095008. Electron impact dissociation of Cl 2 is a key process for the formation of Cl atoms in low-temperature plasmas used for industrial etching processes. Despite this, relatively little cross section data exist for this process. In this work, electron impact dissociation cross sections were calculated for Cl 2 molecules using the UK molecular R-matrix code in the low electron energy range and extended to high energies using a scaling depending on the specific nature of each transition. Our results are compared with both previous calculations and with experimental measurements, and the similarities and differences are discussed. In addition, the rate coefficients for electron impact dissociation of Cl 2 are calculated by integrating the cross sections derived in this (and previous) work, with electron energy distribution functions representative of those normally found in low-temperature plasmas used in industry. Depending on the shape and effective temperature of the distribution function, significant differences arise between the rate coefficients calculated from our cross sections and those calculated using previous data. Deviations between the two sets of rate coefficients are particularly pronounced at the low electron temperatures typical of electron beam and remote plasma sources of interest for atomic layer etching and deposition. These differences are principally caused by the higher energy resolution in the near-threshold region in this work, emphasising the importance of accurate, high-resolution cross sections in this energy range. (10.1088/1361-6595/aada32)
  DOI : 10.1088/1361-6595/aada32
• Local energy transfer rate and kinetic signatures in solar wind turbulence
  
  • Sorriso-Valvo L.
  • Catapano F.
  • Retinò Alessandro
  • Greco A.
  • Perri S.
  • Marino R.
  • Pezzi O.
  • Perrone D.
  • Bruno Roberto
  • Valentini F.
  • Servidio S.
  • Panebianco V.
  , 2018, 20, pp.EGU2018-6552. The transfer of energy from large to small scales in space turbulence is an important ingredient of the longstanding question about the mechanism of the interplanetary plasma heating. Statistical analysis in the context of magnetohydrodynamic (MHD) turbulence provided evidence that the total transported energy is compatible with the observed heating of the solar wind as it expands in the heliosphere. However, in order to understand which processes contribute to the plasma heating, it is necessary to have a local description of the energy flux across scales. To this aim, we propose a proxy of the scale-dependent, local energy transfer that includes magnetic, velocity and cross-helicity terms, and is based on the third-order moment scaling law for MHD turbulence. Data from Helios2 are used to determine the statistical properties of such a proxy in comparison with the magnetic and velocity fields PVI, and the correlation with local solar wind heating is pointed out. MMS data are used to study the correlation with kinetic-scale features, as for example the temperature anisotropy, the heat flux, the agyrothropy of the pressure tensor, and the deviation form Maxwellian. A comparison with hybrid direct numerical simulations of the Vlasov-Maxwell system, including alpha particles, is also performed. The good correlation between the turbulent local energy flux and the indicators of kinetic processes found in the data and in the simulations suggests an important role played by this proxy in the study of plasma energy dissipation.
• The Properties of Lion Roars and Electron Dynamics in Mirror Mode Waves Observed by the Magnetospheric MultiScale Mission
  
  • Breuillard Hugo
  • Le Contel Olivier
  • Chust Thomas
  • Berthomier Matthieu
  • Retinò Alessandro
  • Turner D. L.
  • Nakamura R.
  • Baumjohann W.
  • Cozzani Giulia
  • Catapano F.
  • Alexandrova Alexandra
  • Mirioni Laurent
  • Graham D. B.
  • Argall M. R.
  • Fischer D.
  • Wilder F. D.
  • Gershman D. J.
  • Varsani A.
  • Lindqvist P.-A.
  • Khotyaintsev Y. V.
  • Marklund G.
  • Ergun R. E.
  • Goodrich K. A.
  • Ahmadi N.
  • Burch J. L.
  • Torbert R. B.
  • Needell G.
  • Chutter M.
  • Rau D.
  • Dors I.
  • Russell C. T.
  • Magnes W.
  • Strangeway R. J.
  • Bromund K. R.
  • Wei H.
  • Plaschke F.
  • Anderson B. J.
  • Le G.
  • Moore T. E.
  • Giles B. L.
  • Paterson W. R.
  • Pollock C. J.
  • Dorelli J. C.
  • Avanov L. A.
  • Saito Y.
  • Lavraud B.
  • Fuselier S. A.
  • Mauk B. H.
  • Cohen I. J.
  • Fennell J. F.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2018, 123 (1), pp.93-103. Mirror mode waves are ubiquitous in the Earth's magnetosheath, in particular behind the quasi-perpendicular shock. Embedded in these nonlinear structures, intense lion roars are often observed. Lion roars are characterized by whistler wave packets at a frequency 100 Hz, which are thought to be generated in the magnetic field minima. In this study, we make use of the high time resolution instruments on board the Magnetospheric MultiScale mission to investigate these waves and the associated electron dynamics in the quasi-perpendicular magnetosheath on 22 January 2016. We show that despite a core electron parallel anisotropy, lion roars can be generated locally in the range 0.05-0.2f<SUB>ce</SUB> by the perpendicular anisotropy of electrons in a particular energy range. We also show that intense lion roars can be observed up to higher frequencies due to the sharp nonlinear peaks of the signal, which appear as sharp spikes in the dynamic spectra. As a result, a high sampling rate is needed to estimate correctly their amplitude, and the latter might have been underestimated in previous studies using lower time resolution instruments. We also present for the first-time 3-D high time resolution electron velocity distribution functions in mirror modes. We demonstrate that the dynamics of electrons trapped in the mirror mode structures are consistent with the Kivelson and Southwood (1996) model. However, these electrons can also interact with the embedded lion roars: first signatures of electron quasi-linear pitch angle diffusion and possible signatures of nonlinear interaction with high-amplitude wave packets are presented. These processes can lead to electron untrapping from mirror modes. (10.1002/2017JA024551)
  DOI : 10.1002/2017JA024551
• Ionospheric climatology at Africa EIA trough stations during descending phase of sunspot cycle 22
  
  • Abedesin B.O.
  • Rabiu A. B.
  • Bolaji O. S.
  • Amory-Mazaudier Christine
  Journal of Atmospheric and Solar-Terrestrial Physics, Elsevier, 2018, 172, pp.83-99. The African equatorial ionospheric climatology during the descending phase of sunspot-cycle 22 (spanning 19921996) was investigated using 3 ionosondes located at Dakar (14.70 N, 342.60 E), Ouagadougou (12.420 N, 358.60 E), and Korhogo (9.510 N, 354.40 E). The variations in the virtual height of the F-layer (hF), maximum electron density (NmF2), vertical plasma drift (Vp) and zonal electric field (Ey) were presented. Significant decrease in the NmF2 amplitude compared to hF in all of the stations during the descending period is obvious. While NmF2 magnitude maximizes/minimizes during the E-seasons/J-season, hF attained highest/lowest altitude in J-season/D-season for all stations. D-season anomaly was evident in NmF2 at all stations. For any season, the intensity (Ibt) of NmF2 noon-bite-out is highest at Dakar owning to fountain effect and maximizes in March-E season. Stations across the EIA trough show nearly coherence ionospheric climatology characteristics whose difference is of latitudinal origin. Hemispheric dependence in NmF2 is obvious, with difference more significant during high-solar activity and closes with decreasing solar activity. The variability in the plasma drift during the entire phase is suggested to emanate from solar flux variations, and additionally from enhanced leakage of electric fields from high-to low-latitudes. Existing African regional model of evening/nightttime pre-reversal plasma drift/ sunspot number (PRE peak/R) relationship compares well with experimental observations at all stations with slight over-estimation. The correlation/root-mean-square-deviation (RMS dev) pair between the model and observed Vp during the descending phase recorded 94.9%/0.756, 92.4%/1.526, and 79.1%/3.612 at Korhogo, Ouagadougou and Dakar respectively. The Ey/hF and Ey/NmF2 relationships suggest that zonal electric field is more active in the lifting of hF and suppression of NmF2 during high- and moderate-solar activities when compared with low solar activity. This is the first work to show higher bite-out at the equatorial northern-station (Dakar) than southern-station (Korhogo) using ionosonde data. (10.1016/j.jastp.2018.03.009)
  DOI : 10.1016/j.jastp.2018.03.009
• Magnetic Reconnection, Turbulence, and Particle Acceleration: Observations in the Earth's Magnetotail
  
  • Ergun R. E.
  • Goodrich K. A.
  • Wilder F. D.
  • Ahmadi N.
  • Holmes J. C.
  • Eriksson S.
  • Stawarz J. E.
  • Nakamura R.
  • Genestreti K. J.
  • Hesse Michael
  • Burch J. L.
  • Torbert R. B.
  • Phan T. D.
  • Schwartz S. J.
  • Eastwood Jonathan P.
  • Strangeway R. J.
  • Le Contel Olivier
  • Russell C. T.
  • Argall M. R.
  • Lindqvist P.-A.
  • Chen L. J.
  • Cassak P. A.
  • Giles B. L.
  • Dorelli J. C.
  • Gershman D. J.
  • Leonard T. W.
  • Lavraud B.
  • Retinò Alessandro
  • Matthaeus W. H.
  • Vaivads A.
  Geophysical Research Letters, American Geophysical Union, 2018, 45, pp.3338-3347. We report observations of turbulent dissipation and particle acceleration from large-amplitude electric fields (E) associated with strong magnetic field (B) fluctuations in the Earth's plasma sheet. The turbulence occurs in a region of depleted density with anti-earthward flows followed by earthward flows suggesting ongoing magnetic reconnection. In the turbulent region, ions and electrons have a significant increase in energy, occasionally >100 keV, and strong variation. There are numerous occurrences of |E| >100 mV/m including occurrences of large potentials (>1 kV) parallel to B and occurrences with extraordinarily large J · E (J is current density). In this event, we find that the perpendicular contribution of J · E with frequencies near or below the ion cyclotron frequency (f<SUB>ci</SUB>) provide the majority net positive J · E. Large-amplitude parallel E events with frequencies above f<SUB>ci</SUB> to several times the lower hybrid frequency provide significant dissipation and can result in energetic electron acceleration. (10.1002/2018GL076993)
  DOI : 10.1002/2018GL076993
• Localized Oscillatory Energy Conversion in Magnetopause Reconnection
  
  • Burch J. L.
  • Ergun R. E.
  • Cassak P. A.
  • Webster J. M.
  • Torbert R. B.
  • Giles B. L.
  • Dorelli J. C.
  • Rager A. C.
  • Hwang K.-J.
  • Phan T. D.
  • Genestreti K. J.
  • Allen R. C.
  • Chen L.-J.
  • Wang S.
  • Gershman D. J.
  • Le Contel Olivier
  • Russell C. T.
  • Strangeway R. J.
  • Wilder F. D.
  • Graham D. B.
  • Hesse Michael
  • Drake J. F.
  • Swisdak M.
  • Price L. M.
  • Shay M. A.
  • Lindqvist P.-A.
  • Pollock C. J.
  • Denton R. E.
  • Newman D. L.
  Geophysical Research Letters, American Geophysical Union, 2018, 45 (3), pp.1237-1245. Data from the NASA Magnetospheric Multiscale mission are used to investigate asymmetric magnetic reconnection at the dayside boundary between the Earth's magnetosphere and the solar wind. High-resolution measurements of plasmas and fields are used to identify highly localized ( 15 electron Debye lengths) standing wave structures with large electric field amplitudes (up to 100 mV/m). These wave structures are associated with spatially oscillatory energy conversion, which appears as alternatingly positive and negative values of J · E. For small guide magnetic fields the wave structures occur in the electron stagnation region at the magnetosphere edge of the electron diffusion region. For larger guide fields the structures also occur near the reconnection X-line. This difference is explained in terms of channels for the out-of-plane current (agyrotropic electrons at the stagnation point and guide field-aligned electrons at the X-line). (10.1002/2017GL076809)
  DOI : 10.1002/2017GL076809
• Production of hydrogen negative ions in an ECR volume source: balance between vibrational excitation and ionization
  
  • Aleiferis S.
  • Svarnas P.
  • Béchu S.
  • Tarvainen O.
  • Bacal M.
  Plasma Sources Science and Technology, IOP Publishing, 2018, 27 (7), pp.075015. The operation of an ECR-driven (2.45 GHz) hydrogen negative ion source is studied. Electron densities and temperatures are investigated with electrostatic probes and negative ion densities are measured with laser photodetachment. Vacuum ultraviolet irradiance measurements are focused on molecular transitions to the ground state while high-resolution visible emission spectroscopy is used to study the transitions between excited states for both molecules and atoms. The standalone operation of the source is found to be more efficient in higher pressures (12 mTorr) where negative ion densities are as high as 4×109 cm−3. Further investigation on the operation of the source reveals a rich vibrational spectrum. On the other hand, a limitation on the production of negative ions which is attributed to a lack of low-energy electrons becomes apparent. The underlying mechanisms that lead to this behavior are discussed along with possible solutions to this issue. Finally, the rates of different negative ion destruction processes are estimated and compared. (10.1088/1361-6595/aabf1b)
  DOI : 10.1088/1361-6595/aabf1b
• Plasma acceleration on multiscale temporal variations of electric and magnetic fields during substorm dipolarization in the Earth’s magnetotail
  
  • Parkhomenko Elena
  • Vitalevna-Malova Helmi
  • Evgenevna-Grigorenko Elena
  • Yurevich-Popov Victor
  • Alekseevich-Petrukovich Anatolii
  • Delcourt Dominique C.
  • Aleksandrovna-Kronberg Elena
  • Daly Patrick W.
  • Matveevich-Zelenyi Lev
  Annals of Geophysics, Istituto Nazionale di Geofisica e Vulcanologia (INGV), 2018, 61 (3), pp.GM334. Magnetic field dipolarizations are often observed in the magnetotail during substorms. These generally include three temporal scales: (1) actual dipolarization when the normal magnetic field changes during several minutes from minimum to maximum level; (2) sharp Bz bursts (pulses) interpreted as the passage of multiple dipolarization fronts with characteristic time scales < 1 min, and (3) bursts of electric and magnetic fluctuations with frequencies up to electron gyrofrequency occurring at the smallest time scales (≤ 1 s). We present a numerical model where the contributions of the above processes (1)-(3) in particle acceleration are analyzed. It is shown that these processes have a resonant character at different temporal scales. While O+ ions are more likely accelerated due to the mechanism (1), H+ ions (and to some extent electrons) are effectively accelerated due to the second mechanism. High-frequency electric and magnetic fluctuations accompanying magnetic dipolarization as in (3) are also found to efficiently accelerate electrons. (10.4401/ag-7582)
  DOI : 10.4401/ag-7582
• Perpendicular Current Reduction Caused by Cold Ions of Ionospheric Origin in Magnetic Reconnection at the Magnetopause: Particle‐in‐Cell Simulations and Spacecraft Observations
  
  • Toledo‐redondo Sergio
  • Dargent Jérémy
  • Aunai Nicolas
  • Lavraud Benoit
  • André Mats
  • Li Wenya
  • Giles Barbara
  • Lindqvist Per‐arne
  • Ergun Robert
  • Russell Christopher
  • Burch James
  Geophysical Research Letters, American Geophysical Union, 2018, 45 (19), pp.10,033-10,042. Cold ions of ionospheric origin are present throughout the Earth's magnetosphere, including the dayside magnetopause, where they modify the properties of magnetic reconnection, a major coupling mechanism at work between the magnetosheath and the magnetosphere. We present Magnetospheric MultiScale (MMS) spacecraft observations of the reconnecting magnetopause with different amounts of cold ions and show that their presence reduces the Hall term in the Ohm's law. Then, we compare two particle-in-cell simulations, with and without cold ions on the magnetospheric side. The cold ions remain magnetized inside the magnetospheric separatrix region, leading to the reduction of the perpendicular currents associated with the Hall effect. Moreover, this reduction is proportional to the relative number density of cold ions. And finally, the Hall electric field peak is reduced along the magnetospheric separatrix owing to cold ions. This should have an effect on energy conversion by reconnection from electromagnetic fields to kinetic energy of the particles (10.1029/2018GL079051)
  DOI : 10.1029/2018GL079051
• Du plasma dans l'espace ?
  
  • Rezeau Laurence
  Le Bulletin de l'Union des Professeurs de Physique et de Chimie, Union des professeurs de physique et de chimie, 2018 (1000), pp.153-162. Le mot plasma n'évoque pas d'abord l'espace, mais plutôt la médecine ou les écrans de télévision. Pourtant, le quatrième état de la matière constitue l'essentiel de la matière connue de l'Univers. Le milieu interplanétaire est un plasma, de même que l'environnement de la Terre au-dessus de quelques centaines de kilomètres. On a découvert ces plasmas au début du XXème siècle et on les explore depuis les débuts de l'ère spatiale. Les découvertes en physique des plasmas spatiaux sont donc fortement liées à l'exploration du Système solaire par les missions spatiales. Le Soleil interagit avec la Terre en l'éclairant, mais pas seulement ! Il éjecte aussi un vent de plasma qui nous bombarderait si nous n'avions pas un bouclier protecteur plutôt efficace, le champ magnétique terrestre. On sait maintenant faire le lien entre les éjections de plasma observées sur le Soleil et les magnifiques aurores boréales observées au sol.
• Electron magnetic reconnection without ion coupling in Earth's turbulent magnetosheath
  
  • Phan T. D.
  • Eastwood Jonathan P.
  • Shay M. A.
  • Drake J. F.
  • Sonnerup B. U. Ö.
  • Fujimoto M.
  • Cassak P. A.
  • Oieroset M.
  • Burch J. L.
  • Torbert R. B.
  • Rager A. C.
  • Dorelli J. C.
  • Gershman D. J.
  • Pollock C.
  • Pyakurel P. S.
  • Haggerty C. C.
  • Khotyaintsev Y. V.
  • Lavraud B.
  • Saito Y.
  • Oka M.
  • Ergun R. E.
  • Retinò Alessandro
  • Le Contel Olivier
  • Argall M. R.
  • Giles B. L.
  • Moore T. E.
  • Wilder F. D.
  • Strangeway R. J.
  • Russell C. T.
  • Lindqvist P. A.
  • Magnes W.
  Nature, Nature Publishing Group, 2018, 557, pp.202-206. Magnetic reconnection in current sheets is a magnetic-to-particle energy conversion process that is fundamental to many space and laboratory plasma systems. In the standard model of reconnection, this process occurs in a minuscule electron-scale diffusion region(1,2). On larger scales, ions couple to the newly reconnected magnetic-field lines and are ejected away from the diffusion region in the form of bi-directional ion jets at the ion Alfven speed(3-5). Much of the energy conversion occurs in spatially extended ion exhausts downstream of the diffusion region(6). In turbulent plasmas, which contain a large number of small-scale current sheets, reconnection has long been suggested to have a major role in the dissipation of turbulent energy at kinetic scales(7-11). However, evidence for reconnection plasma jetting in small-scale turbulent plasmas has so far been lacking. Here we report observations made in Earth's turbulent magnetosheath region (downstream of the bow shock) of an electron-scale current sheet in which diverging bi-directional super-ion-Alfvenic electron jets, parallel electric fields and enhanced magnetic-to-particle energy conversion were detected. Contrary to the standard model of reconnection, the thin reconnecting current sheet was not embedded in a wider ion-scale current layer and no ion jets were detected. Observations of this and other similar, but unidirectional, electron jet events without signatures of ion reconnection reveal a form of reconnection that can drive turbulent energy transfer and dissipation in electron-scale current sheets without ion coupling. (10.1038/s41586-018-0091-5)
  DOI : 10.1038/s41586-018-0091-5