Publications

2023

• Multi-periodic and random mode of Atmospheric Pressure Plasma Jets and their interactions with liquid and biological target
  
  • Yang Hang
  , 2023. Atmospheric Pressure Plasma Jets (APPJ) have been intensively studied due to their numerous applications, especially for medical applications such as wound healing or tumor reduction. In this thesis, multi-periodic and random modes of propagation are observed in an APPJ. The role of surface charges is addressed. The interaction between the APPJ and liquid targets or inert porcine skin samples is investigated.A helium APPJ with different electrode configurations is driven by 15~18 kHz sinusoidal voltage I; it ignites multi-periodic self-triggered mode or random mode depending on the applied voltage, driven frequency and inter-electrode gap distance. The presence of an outer grounded electrode ring with an inter-electrode gap distance of 2 cm ~ 4 cm is a key parameter permitting the ignition of multiperiodic discharges when the gap distance between the high voltage electro and this grounded electrode is longer than 20 mm. Most of the observed multi-periodic discharges operate every 2 or 3 sinusoidal periods and are 8 times longer than the ones propagating in random mode. Such discharges show similarities with pulsed operating mode, having a jitter smaller than 100 ns. Fast imaging reveals that 2-3 self-triggered discharges occur in the gap region prior to ignition of the bullet-like discharge in both positive or negative polarities; this leads to an accumulation of charges beneath the ground electrode, locally enhancing the electric field. Bullet velocities for different polarities and gap distances are compared using optical emission spectrum. Discharges in random mode are studied with a 5 mm int er-electrode gap distance. Multiple consecutive discharges are observed. Long random discharges are ignited after short periodic discharges. The velocity of random long bullets is measured statistically.APPJ is used to treat water targets and inert porcine skin samples. The propagation of this APPJ shows similar multi-periodic modes and random modes. The upstream propagation shows an influence on the downstream propagation. The H2O2 production rate is measured by varying the voltage, the target distance and the Helium flow rate. Defrost pig skin is treated by the APPJ and analyzed by full-field Mueller polarimetric imaging (MPI) within 30 minutes. Above 0.5 W / 4 min static treatment, NTP is shown to modify the linear phase retardance and the total depolarization. The tissue modifications are inhomogeneous and present distinct features at the center and the fringes of the plasma-treated area. According to control groups, tissue alterations are primarily caused by the local heating concomitant to plasma-skin interaction (typically 45-73℃). On the other hand, no tissue alteration is detected at 0.3 W (35℃) treatment. This study aims to show that full-field MPI is suitable for fast and without-contact detection of skin microstructure modifications induced by plasma treatment.
• Interaction dust–plasma in Titan's ionosphere: Feedbacks on the gas phase composition
  
  • Chatain Audrey
  • Carrasco Nathalie
  • Vettier Ludovic
  • Guaitella Olivier
  Icarus, Elsevier, 2023, 396 (May), pp.115502. Titan's organic aerosols are formed and spend some time in the ionosphere, an atmospheric layer ionized by solar VUV photons and energetic particles coming from the magnetosphere of Saturn, forming a natural N2-CH4-H2 plasma. Previous works showed some chemical evolution processes: VUV photons slightly alter the aerosols nitrile bands, hydrogen atoms tend to hydrogenate their surface and carbon-containing species participate to the growth of the aerosols. This work investigates the effect of the other plasma species, neglected until now, namely the N2-H2 derived ions, radicals and electronic or vibrational excited states. Industrial plasmas often use N2-H2 discharges to form ammonia-based fertilizers, for metal nitriding, and to erode organic surfaces. Consequently, these are likely to affect Titan's organic aerosols. We therefore developed the THETIS experiment (for Tholin Evolution in Titan's Ionosphere Simulation) to study the interactions between analogues of Titan's aerosols (tholins) and the erosive N2-H2 plasma species found in Titan's ionosphere. Following a first paper on the investigation of the evolution of the solid phase by Scanning Electron Microscopy and IR transmission spectroscopy (Chatain et al., 2020a), this second paper focuses on evolution of the gas phase composition, studied by neutral and ion mass spectrometry. In the presented experiments, newly formed HCN, NH3-CN and C2N2 are extracted in quantity from the tholins as well as some other carbon-containing species and their derived ions. On the other hand, the production of ammonia strongly decreases, probably because the H, NH and N radicals are rather used for the production of HCN at the surface of tholins. Heterogeneous processes are suggested based on the experimental observations: chemical processes induced by radicals at the surface would modify and weaken the tholin structure, while ion sputtering would desorb small molecules and highly unsaturated ions. The effect of plasma erosion on aerosols in Titan's ionosphere could therefore lead to the formation of Ctriple bondN bonds in the aerosol structure, as well as the production of HCN or R-CN species in the gas phase. (10.1016/j.icarus.2023.115502)
  DOI : 10.1016/j.icarus.2023.115502
• Two-photon absorption laser induced fluorescence (TALIF) detection of atomic iodine in low-temperature plasmas and a revision of the energy levels of I I
  
  • Esteves Benjamin
  • Blondel Christophe
  • Chabert Pascal
  • Drag Cyril
  Journal of Physics B: Atomic, Molecular and Optical Physics, IOP Publishing, 2023, 56 (5), pp.055002. Abstract In order to perfect the use of iodine, instead of xenon, in plasma thrusters, an experiment has been set up to investigate the feasibility of two-photon absorption laser induced fluorescence (TALIF) diagnostics in iodine plasmas. Levels ( 3 P 2 ) 6 p 2 [ 1 ] 3 / 2 o and ( 3 P 2 ) 6 p 2 [ 3 ] 7 / 2 o of atomic iodine were found qualified for that purpose, with a radiative lifetime of the former found equal to 35.5 ( 9 ) n s , which appears consistent with the 32.5 ( 1.2 ) n s predicted by the most recent calculations. Doppler-free two-photon spectroscopy has confirmed that the relative intensities of the hyperfine components follow well-known general formulas, which makes it possible to disentangle the hyperfine structure of 127 I from Doppler broadening. Accurate temperature measurements are shown to be possible, even though the relatively heavy mass of the iodine atom does not make it the most favorable gauge for measurements based on Doppler effect. Using an injection seeded pulsed laser as the primary laser source, the frequency-tripling of which has provided the ca 300 nm radiation used for excitation, absolute energy measurements of the two-photon excited levels revealed that all upper energy levels of I I have to be revised down, by − 0.169 ( 11 ) c m − 1 , which pulls every energy level off its presently tabulated value by more than thirty times the currently admitted uncertainty bar. (10.1088/1361-6455/acb7b6)
  DOI : 10.1088/1361-6455/acb7b6
• Impact of magnetic ripple on neoclassical equilibrium in gyrokinetic simulations
  
  • Varennes R
  • Garbet X
  • Vermare L.
  • Sarazin Y
  • Dif-Pradalier Guilhem
  • Grandgirard V
  • Ghendrih P
  • Donnel P
  • Peret M
  • Obrejan K
  • Bourne E
  Plasma Physics and Controlled Fusion, IOP Publishing, 2023, 65 (3), pp.035016. Abstract The effect of magnetic field ripple on tokamak plasma without turbulence is studied numerically and augmented with a reduced analytical model that includes neoclassical processes in the presence of non-axisymmetric perturbation and stochastic transport. For this study, a magnetic field ripple perturbation has been implemented in the GYSELA gyrokinetic code. This implementation has been verified thanks to a test of toroidal angular momentum conservation. The GYSELA code was then successfully benchmarked against the NEO code, which solves the drift kinetic equation, and against the reduced model in the collisionality range ν ⋆ ∈ [0.05–0.5] for several amplitudes of the magnetic ripple. An observation, shared by the model, the NEO code and GYSELA simulations is that the thermal drive of the mean poloidal velocity—measured by the k V P coefficient—decreases sharply for large yet experimentally relevant magnetic ripple amplitudes, and may even change sign. (10.1088/1361-6587/acb79a)
  DOI : 10.1088/1361-6587/acb79a
• Study of vibrational kinetics of CO 2 and CO in CO 2 –O 2 plasmas under non-equilibrium conditions
  
  • Fromentin C
  • Silva T
  • Dias T
  • Morillo-Candas A
  • Biondo O
  • Guaitella O
  • Guerra V
  Plasma Sources Science and Technology, IOP Publishing, 2023, 32 (2), pp.024001. Abstract This work explores the effect of O 2 addition on CO 2 dissociation and on the vibrational kinetics of CO 2 and CO under various non-equilibrium plasma conditions. A self-consistent model, previously validated for pure CO 2 discharges, is further extended by adding the vibrational kinetics of CO, including electron impact excitation and de-excitation (e-V), vibration-to-translation relaxation (V-T) and vibration-to-vibration energy exchange (V-V) processes. The vibrational kinetics considered include levels up to v = 10 for CO and up to v 1 = 2 and v 2 = v 3 = 5, respectively for the symmetric stretch, bending and asymmetric stretch modes of CO 2 , and accounts for e-V, V-T in collisions between CO, CO 2 and O 2 molecules and O atoms and V-V processes involving all possible transfers involving CO 2 and CO molecules. The kinetic scheme is validated by comparing the model predictions with recent experimental data measured in a DC glow discharge ignited in pure CO 2 and CO 2 –O 2 , operating at pressures in the range 0.4–5 Torr (53.33–666.66 Pa). The experimental results show a lower vibrational temperature of the different modes of CO 2 and a decreased dissociation fraction of CO 2 when O 2 is added to the plasma but an increase of the vibrational temperature of CO. On the one hand, the simulations suggest that the former effect is the result of the stronger V-T energy-transfer collisions with O atoms which leads to an increase of the relaxation of the CO 2 vibrational modes. On the other hand, two main mechanisms contribute to the lower CO 2 dissociation fraction with increased O 2 content in the mixture: the back reaction, CO(a 3 Π r ) + O 2 → CO 2 + O and the recombinative detachment O − + CO → e + CO 2 . (10.1088/1361-6595/acb665)
  DOI : 10.1088/1361-6595/acb665
• Investigation of multi-periodic self-trigger plasma in an AC-driven atmospheric pressure plasma jet
  
  • Yang Hang
  • Rousseau Antoine
  Plasma Sources Science and Technology, IOP Publishing, 2023, 32 (1), pp.015011. Abstract Atmospheric Pressure Plasma Jets have been intensively studied due to their potential application in biological fields but some of their physics properties are still not well understood. In the present article, a helium plasma jet driven by 15–18 kHz sinusoidal voltage ignites multi-periodic self-triggered mode or random mode depending on the applied voltage, driven frequency and inter-electrode gap distance. Most of the observed multiperiodic bullets operate every 2 or 3 sinusoidal periods. Such bullets show similarities with pulsed operating mode, having a jitter of less than 100 ns. The presence of an outer grounded electrode ring is a key parameter permitting the ignition of multiperiodic bullets; it also enhances the propagation length up to 8 times. Fast imaging reveals that 2–3 self-triggered discharges occur in the gap region prior to ignition of the bullet in both positive or negative polarities; this leads to an accumulation of charges beneath the ground electrode, locally enhancing the electric field. Bullet velocities for different polarities and gap distances are compared using optical emission spectrum. (10.1088/1361-6595/acb461)
  DOI : 10.1088/1361-6595/acb461
• Molecular acclimation of Halobacterium salinarum to halite brine inclusions
  
  • Favreau Charly
  • Tribondeau Alicia
  • Marugan Marie
  • Guyot François
  • Alpha-Bazin Beatrice
  • Marie Arul
  • Puppo Remy
  • Dufour Thierry
  • Huguet Arnaud
  • Zirah Séverine
  • Kish Adrienne
  Frontiers in Microbiology, Frontiers Media, 2023, 13, pp.1075274. Halophilic microorganisms have long been known to survive within the brine inclusions of salt crystals, as evidenced by the change in color for salt crystals containing pigmented halophiles. However, the molecular mechanisms allowing this survival has remained an open question for decades. While protocols for the surface sterilization of halite (NaCl) have enabled isolation of cells and DNA from within halite brine inclusions, “-omics” based approaches have faced two main technical challenges: (1) removal of all contaminating organic biomolecules (including proteins) from halite surfaces, and (2) performing selective biomolecule extractions directly from cells contained within halite brine inclusions with sufficient speed to avoid modifications in gene expression during extraction. In this study, we tested different methods to resolve these two technical challenges. Following this method development, we then applied the optimized methods to perform the first examination of the early acclimation of a model haloarchaeon ( Halobacterium salinarum NRC-1) to halite brine inclusions. Examinations of the proteome of Halobacterium cells two months post-evaporation revealed a high degree of similarity with stationary phase liquid cultures, but with a sharp down-regulation of ribosomal proteins. While proteins for central metabolism were part of the shared proteome between liquid cultures and halite brine inclusions, proteins involved in cell mobility (archaellum, gas vesicles) were either absent or less abundant in halite samples. Proteins unique to cells within brine inclusions included transporters, suggesting modified interactions between cells and the surrounding brine inclusion microenvironment. The methods and hypotheses presented here enable future studies of the survival of halophiles in both culture model and natural halite systems. (10.3389/fmicb.2022.1075274)
  DOI : 10.3389/fmicb.2022.1075274
• Locality of triad interaction and Kolmogorov constant in inertial wave turbulence
  
  • David Vincent
  • Galtier Sébastien
  Journal of Fluid Mechanics, Cambridge University Press (CUP), 2023, 955, pp.R2. Using the theory of wave turbulence for rapidly rotating incompressible fluids derived by Galtier ( Phys. Rev. E, vol. 68, 2003, 015301), we find the locality conditions that the solutions of the kinetic equation must satisfy. We show that the exact anisotropic Kolmogorov–Zakharov spectrum satisfies these conditions, which justifies the existence of this constant (positive) energy flux solution. Although a direct cascade is predicted in the transverse ( $\perp$ ) and parallel ( $\parallel$ ) directions to the rotation axis, we show numerically that in the latter case some triadic interactions can have a negative contribution to the energy flux, while in the former case all interactions contribute to a positive flux. Neglecting the parallel energy flux, we estimate the Kolmogorov constant at $C_K \simeq 0.749$ . These results provide theoretical support for recent numerical and experimental studies. (10.1017/jfm.2022.1073)
  DOI : 10.1017/jfm.2022.1073
• What can we learn from the acceleration and escape of particles from 3D MHD models ?
  
  • Masson Sophie
  , 2023.
• Topology of Magnetic and Velocity Fields at Kinetic Scales in Incompressible Plasma Turbulence
  
  • Zhang J.
  • Huang S.
  • Sahraoui F.
  • Andrés N.
  • Yuan Z.
  • Jiang K.
  • Xu S.
  • Wei Y.
  • Xiong Q.
  • Wang Z.
  • Lin R.
  • Yu L.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2023, 128 (1). Abstract The topology of the magnetic and velocity fields at the kinetic scales are investigated in the context of nearly incompressible magnetosheath plasma turbulence. Using the unprecedented high‐resolution data from the Magnetospheric MultiScale mission, the joint probability distribution functions of geometrical invariants characterizing the magnetic and velocity fields gradient tensor at the kinetic scales are computed. The topological features of the magnetic and velocity field gradient tensors and their symmetric component tensors present axisymmetric distribution patterns, indicating that the structure of the plasma turbulence at the kinetic scales are different from those in hydrodynamic and magnetohydrodynamic turbulence. Moreover, a strong correlation between the straining and rotational parts of the magnetic and velocity field gradient tensors was found, which manifests the dominance of sheet‐like structures at the kinetic‐scales dissipation in incompressible plasma turbulence. (10.1029/2022JA031064)
  DOI : 10.1029/2022JA031064
• Direct evidence of substorm-related impulsive injections of electrons at Mercury
  
  • Aizawa Sae
  • Harada Yuki
  • André Nicolas
  • Saito Yoshifumi
  • Barabash Stas
  • Delcourt Dominique
  • Sauvaud Jean-André
  • Barthe Alain
  • Fedorov Andréi
  • Penou Emmanuel
  • Yokota Shoichiro
  • Miyake Wataru
  • Persson Moa
  • Nénon Quentin
  • Rojo Mathias
  • Futaana Yoshifumi
  • Asamura Kazushi
  • Shimoyama Manabu
  • Hadid L. Z.
  • Fontaine D.
  • Katra Bruno
  • Fraenz Markus
  • Krupp Norbert
  • Matsuda Shoya
  • Murakami Go
  Nature Communications, Nature Publishing Group, 2023, 14 (1), pp.4019. Mercury’s magnetosphere is known to involve fundamental processes releasing particles and energy like at Earth due to the solar wind interaction. The resulting cycle is however much faster and involves acceleration, transport, loss, and recycling of plasma. Direct experimental evidence for the roles of electrons during this cycle is however missing. Here we show that in-situ plasma observations obtained during BepiColombo’s first Mercury flyby reveal a compressed magnetosphere hosts of quasi-periodic fluctuations, including the original observation of dynamic phenomena in the post-midnight, southern magnetosphere. The energy-time dispersed electron enhancements support the occurrence of substorm-related, multiple, impulsive injections of electrons that ultimately precipitate onto its surface and induce X-ray fluorescence. These observations reveal that electron injections and subsequent energy-dependent drift now observed throughout Solar System is a universal mechanism that generates aurorae despite the differences in structure and dynamics of the planetary magnetospheres. (10.1038/s41467-023-39565-4)
  DOI : 10.1038/s41467-023-39565-4
• From Repeatability to Self-Organization of Guided Streamers Propagating in a Jet of Cold Plasma
  
  • Decauchy Henri
  • Dufour Thierry
  plasma, MDPI AG, 2023, 6 (2), pp.250 - 276. In this work, a jet of cold plasma is generated in a device supplied in helium and powered with a high-voltage nanopulse power supply, hence generating guided streamers. We focus on the interaction between these guided streamers and two targets placed in a series: a metal mesh target (MM) at floating potential followed by a metal plate target (MP) grounded by a 1500 Ω resistor. We demonstrate that such an experimental setup allows to shift from a physics of streamer repeatability to a physics of streamer self-organization, i.e., from the repetition of guided streamers that exhibit fixed spatiotemporal constants to the emergence of self-organized guided streamers, each of which is generated on the rising edge of a high-voltage pulse. Up to five positive guided streamers can be self-organized one after the other, all distinct in space and time. While self-organization occurs in the capillary and up to the MM target, we also demonstrate the existence of transient emissive phenomena in the inter-target region, especially a filamentary discharge whose generation is directly correlated with complexity order Ω. The mechanisms of the self-organized guided streamers are deciphered by correlating their optical and electrical properties measured by fast ICCD camera and current-voltage probes, respectively. For the sake of clarity, special attention is paid to the case where three selforganized guided streamers (α, β and γ) propagate at vα = 75.7 km•s-1 , vβ = 66.5 km•s-1 and vγ = 58.2 km•s-1), before being accelerated in the vicinity of the MM target. (10.3390/plasma6020019)
  DOI : 10.3390/plasma6020019
• Stereoscopic disambiguation of vector magnetograms: First applications to SO/PHI-HRT data
  
  • Valori G.
  • Calchetti D.
  • Moreno Vacas A.
  • Pariat É.
  • Solanki S K
  • Löschl P.
  • Hirzberger J.
  • Parenti S.
  • Albert K.
  • Albelo Jorge N.
  • Álvarez-Herrero A.
  • Appourchaux T.
  • Bellot Rubio L R
  • Blanco Rodríguez J.
  • Campos-Jara A.
  • Feller A.
  • Gandorfer A.
  • García Parejo P.
  • Germerott D.
  • Gizon L.
  • Gómez Cama J M
  • Guerrero L.
  • Gutierrez-Marques P.
  • Kahil F.
  • Kolleck M.
  • Korpi-Lagg A.
  • Orozco Suárez D.
  • Pérez-Grande I.
  • Sanchis Kilders E.
  • Schou J.
  • Schühle U.
  • Sinjan J.
  • Staub J.
  • Strecker H.
  • del Toro Iniesta J C
  • Volkmer R.
  • Woch J.
  Astronomy & Astrophysics - A&A, EDP Sciences, 2023, 677, pp.A25. Contact. Spectropolarimetric reconstructions of the photospheric vector magnetic field are intrinsically limited by the 180° ambiguity in the orientation of the transverse component. So far, the removal of such an ambiguity has required assumptions about the properties of the photospheric field, which makes disambiguation methods model-dependent. Aims. The successful launch and operation of Solar Orbiter have made the removal of the 180° ambiguity possible solely using observations of the same location on the Sun obtained from two different vantage points. Methods. The basic idea is that the unambiguous line-of-sight component of the field measured from one vantage point will generally have a nonzero projection on the ambiguous transverse component measured by the second telescope, thereby determining the “true” orientation of the transverse field. Such an idea was developed and implemented as part of the stereoscopic disambiguation method (SDM), which was recently tested using numerical simulations. Results. In this work we present a first application of the SDM to data obtained by the High Resolution Telescope (HRT) on board Solar Orbiter during the March 2022 campaign, when the angle with Earth was 27 degrees. The method was successfully applied to remove the ambiguity in the transverse component of the vector magnetogram solely using observations (from HRT and from the Helioseismic and Magnetic Imager) for the first time. Conclusions. The SDM is proven to provide observation-only disambiguated vector magnetograms that are spatially homogeneous and consistent. A discussion on the sources of error that may limit the accuracy of the method, and strategies to remove them in future applications, is also presented. (10.1051/0004-6361/202345859)
  DOI : 10.1051/0004-6361/202345859
• Streamer-to-filament transition in pulsed nanosecond atmospheric pressure discharge: 2D numerical modelling
  
  • Zhang Bin
  • Zhu Yifei
  • Zhang Xiaobing
  • Popov Nikolay
  • Orrière Thomas
  • Pai David
  • Starikovskaia Svetlana
  Plasma Sources Science and Technology, IOP Publishing, 2023, 32 (11), pp.115014. The streamer-to-filament transition in air at atmospheric pressure, in a nanosecond pin-to-pin discharge, is studied by a 2D model. The main aim is to implement a kinetic scheme providing a sharp electron density increase to the 2D PASSKEy code, to validate the results on the available experimental data, and to investigate the mechanisms responsible for the transition. Results show that after the formation of a conductive channel across the discharge gap, two discharge modes appear during a few nanoseconds: a glow phase, with a relatively homogeneous distribution with the electron density of 1.0 × 10 14 cm-3 , and a filamentary phase, with the electron density of 1.0×10 18 cm −3. Two filaments appear at the cathode and anode respectively, and propagate towards the middle of the gap with a velocity of about 1.1 • 10 7 cm/s, forming a narrow channel. Simultaneously, the gas temperature increases from 350 to 2800 K. The diameter of the channel at the middle gap decreases from 210 to 90 µm. Dissociation and ionization of the electronically excited states of molecules N2(A^3 Σ+u, B3Πg, a ′1Σ − u, C^3Πu), and ionization of ground and electronically excited states of O and N atoms are the most important processes for the transition. Numerical results also reveal the influence of the memory effect (pre-heating, pre-ionization, and predissociation) from previous pulses on the streamer-to-filament transition. (10.1088/1361-6595/ad085c)
  DOI : 10.1088/1361-6595/ad085c
• Ultra-high-resolution observations of persistent null-point reconnection in the solar corona
  
  • Cheng X.
  • Priest E.
  • Li H.
  • Chen J.
  • Aulanier Guillaume
  • Chitta L.
  • Wang Y.
  • Peter H.
  • Zhu X.
  • Xing C.
  • Ding M.
  • Solanki S.
  • Berghmans D.
  • Teriaca L.
  • Aznar Cuadrado R.
  • Zhukov A.
  • Guo Y.
  • Long D.
  • Harra L.
  • Smith P.
  • Rodriguez L.
  • Verbeeck C.
  • Barczynski K.
  • Parenti S.
  Nature Communications, Nature Publishing Group, 2023, 14 (1), pp.2107. Magnetic reconnection is a key mechanism involved in solar eruptions and is also a prime possibility to heat the low corona to millions of degrees. Here, we present ultra-high-resolution extreme ultraviolet observations of persistent null-point reconnection in the corona at a scale of about 390 km over one hour observations of the Extreme-Ultraviolet Imager on board Solar Orbiter spacecraft. The observations show formation of a null-point configuration above a minor positive polarity embedded within a region of dominant negative polarity near a sunspot. The gentle phase of the persistent null-point reconnection is evidenced by sustained point-like high-temperature plasma (about 10 MK) near the null-point and constant outflow blobs not only along the outer spine but also along the fan surface. The blobs appear at a higher frequency than previously observed with an average velocity of about 80 km s −1 and life-times of about 40 s. The null-point reconnection also occurs explosively but only for 4 minutes, its coupling with a mini-filament eruption generates a spiral jet. These results suggest that magnetic reconnection, at previously unresolved scales, proceeds continually in a gentle and/or explosive way to persistently transfer mass and energy to the overlying corona. (10.1038/s41467-023-37888-w)
  DOI : 10.1038/s41467-023-37888-w
• Oxygen atom and ozone kinetics in the afterglow of a pulse-modulated DC discharge in pure O2 : an experimental and modelling study of surface mechanisms and ozone vibrational kinetics
  
  • Booth Jean-Paul
  • Guaitella Olivier
  • Zhang Shu
  • Lopaev Dmitry
  • Zyryanov S
  • Rakhimova T
  • Voloshin D
  • Chukalovsky Alexander
  • Volynets Andrey Vladimirovich
  • Mankelevich Yu
  Plasma Sources Science and Technology, IOP Publishing, 2023, 32 (9), pp.095016. Abstract The chemical kinetics of oxygen atoms and ozone molecules were investigated in a fullymodulated DC discharge in pure oxygen gas in a borosilicate glass tube, using cavity ringdown spectroscopy (CRDS) of the optically forbidden O(3P2)->O(1D2) absorption at 630nm. Measurements were made over a range of tube temperatures (10 and 50°C) gas pressures (0.5-4 Torr) and discharge current (10-40 mA). The discharge current was square-wave modulated (on for 0.2 seconds and off for 1 second), allowing the build-up to steady state and the decay in the-afterglow to be studied. This paper focusses on the afterglow period. The O atom density decays non-exponentially in the afterglow, indicating a surface loss probability dependent on incident active particle fluxes. The oxygen atom absorption peak lies on a time-varying absorption continuum due (in the afterglow) to the Chappuis bands of ozone. The ozone density passes through a maximum a few 100ms into the afterglow, then decays slowly. An existing time-resolved self-consistent 1D radial model of O2 positive column discharges was modified to interpret the new results. The ozone behaviour in the afterglow can only be modelled by the inclusion of : 1) surface production of O3 from the reaction of O2 molecules with adsorbed O atoms, 2) reactions of vibrationally-excited ozone with O atoms and with O2(a1∆g) molecules, and 3) surface loss of ozone with a probability of around 10-5. (10.1088/1361-6595/acf956)
  DOI : 10.1088/1361-6595/acf956
• Firefly: The Case for a Holistic Understanding of the Global Structure and Dynamics of the Sun and the Heliosphere
  
  • Raouafi Nour E.
  • Hoeksema J. Todd
  • Newmark Jeffrey S.
  • Gibson Sarah
  • Berger Thomas E.
  • Upton Lisa A.
  • Vourlidas Angelos
  • Hassler Donald M.
  • Kinnison James
  • Ho George C.
  • Mason Glenn M.
  • Vievering Juliana T.
  • Viall Nicholeen M.
  • Szabo Adam
  • Casti Marta
  • Case Anthony W.
  • Lepri Susan T.
  • Velli Marco
  • Georgoulis Manolis K.
  • Bourouaine Sofiane
  • Jagarlamudi Vamsee K.
  • Laming John M.
  • Mason James P.
  • Harra Louise
  • Madjarska Maria
  • Chitta Lakshmi Pradeep
  • Castellanos Duran J. Sebastian
  • Korpi-Lagg Andreas
  • Badman Samuel
  • Chifu Iulia
  • Lario David
  • Wing Simon
  • Bale Stuart
  • Paouris Evangelos
  • Narayanamurthy Smitha
  • Sinjan Jonas
  • Bernasconi Pietro
  • Krivova Natalie
  • Gizon Laurent
  • Leamon Robert J.
  • Gosain Sanjay
  • Kazachenko Maria
  • Petrie Gordon
  • Martinez Pillet Valentin
  • Jain Kiran
  • Luhmann Janet
  • Bertello Luca
  • Toriumi Shin
  • Jiang Chen
  • Vasko Ivan
  • Harvey John W.
  • Schad Thomas A.
  • Jebaraj Immanuel C.
  • Scherrer Philip
  • Hofmeister Stefan
  • Tiwari Sanjiv
  • Wang Haimin
  • Roth Markus
  • Panesar Navdeep
  • Sekii Takashi
  • Magyar Norbert
  • Guglielmino Salvo L.
  • Parenti Susanna
  • Tremblay Benoit
  • Tziotziou Kostas
  • de Toma Giuliana
  • Chen Bin
  • Katsukawa Yukio
  • de Pontieu Bart
  • Cheng Xin
  • Cheung Mark
  • Kosovichev Alexander
  • Jiang Jie
  • Schunker Hannah
  • Kawabata Yusuke
  • Oba Takayoshi
  • Cameron Robert
  • Mathew Shibu K.
  • de la Cruz Rodriguez Jaime
  • Kusano Kanya
  • Temmer Manuela
  • Andretta Vincenzo
  • Sven Wedemeyer
  • Samara Evangelia
  • Heinemann Stephan G.
  • Warmuth Alexander
  • Jafarzadeh Shahin
  • Mackay Duncan H.
  • Fludra Andrzej
  • Bellot Rubio Luis
  • Orozco Suárez David
  • Chen Thomas Y.
  • Kontogiannis Ioannis
  • Yardley Stephanie
  • Veronig Astrid
  • Joshi Jayant
  • Spadaro Daniele
  • Kubo Masahito
  • Bose Souvik
  • Bello González Nazaret
  • Solanki Sami
  • Denker Carsten
  • Verma Meetu
  • Vocks Christian
  • Borrero Juan Manuel
  • Mathews Nathaniel H.
  • Cury Shannon
  • Sasso Clementina
  • Stenborg Guillermo
  • Tibebu Getachew
  • Battams Karl
  • Wijsen Nicolas
  • Bruno Alessandro
  • Peter Hardi
  • Mason Emily I.
  • Caplan Ronald M.
  • Martinez-Sykora Juan
  • Seaton Daniel
  • Airapetian Vladimir
  • Jian Lan
  • Thompson William T.
  • Ofman Leon
  • Wallace Samantha
  • Kucera Therese
  • Desai Ravindra
  • Richardson Ian
  • Burkepile Joan
  • Cranmer Steven
  • Strauss R. Du Toit
  • Murabito Mariarita
  • Alfred de Wijn
  • Xie Hong
  • Rempel Matthias
  • Hess Webber Shea
  • Reeves Katharine K.
  • Hurlburt Neal
  • Berrilli Francesco
  • Deluca Edward
  • Egeland Ricky
  • Ko Yuan-Kuen
  • Kee Nathaniel Dylan
  • Mahajan Sushant S.
  • Craig Deforest
  • Wood Brian E.
  • Chris Chaston
  • Nigro Giuseppina
  • Shaik Shaheda Begum
  • Gosic Milan
  • Shimizu Toshifumi
  • Zuccarello Francesca
  • Nitta Nariaki
  • Chatzistergos Theodosios
  • Fan Yuhong
  • Zhang Jie
  • Fehlmann Andre
  • Palmerio Erika
  • Ishikawa Ryohtaroh T.
  • Danilovic Sanja
  • Skan Moa
  • Froment Clara
  • Díaz Baso Carlos José
  • Liang Zhi-Chao
  • Dudok de Wit Thierry
  • Barczynski Krzysztof
  • Johnston Craig
  • Pariat Etienne
  • Hadid Lina
  • Aulanier Guillaume
  • Brun Allan Sacha
  • Athanasios Kouloumvakos
  • Cauzzi Gianna
  • Dredger Pauline
  • French Ryan
  • Christian Damian
  • Linton Mark
  • Ireland Jack
  • Tarr Lucas
  • Strugarek Antoine
  • Uritsky Vadim
  • Derosa Marc
  • Kretzschmar Matthieu
  • García Rafael A.
  • Monteiro Mario J. P. F. G.
  • Mathur Savita
  • Breton Sylvain N.
  • Pinto Rui F.
  • Martinez Oliveros Juan Carlos
  • Loper Robert
  • Auchère Frédéric
  • Wang Tongjiang
  • Reginald Nelson
  • Cunha Margarida S.
  • Teriaca Luca
  • Chintzoglou Georgios
  • Lynch Benjamin J.
  • Linker Jon
  • Beck Paul
  • Shannon Jackson
  • Clare Benjamin
  • Krupiarz Christopher
  • Whiting Ian D.
  • Byerly Adam
  • Bushman Stewart
  • Carrelli David
  • Kijewski Seth
  • Englander Jacob
  • Mizes Adam
  • Porter Jamie
  • O'Neill Michael
  • Chattopadhyay Debarati
  • Albers Joshua
  • Rast Mark
  • Ermolli Ilaria
  • Tzeng Nigel
  • Hudson James F.
  • Giunta Alessandra
  • Buchlin Éric
  • Bommier Véronique
  • Duncan Nicole
  • Janvier Miho
  • Strecker Hanna
  • Siu Azaymi
  • Perri Barbara
  • Maksimovic Milan
  • Vilmer Nicole
  • Toledo-Redondo Sergio
  • Kuckein Christoph
  • Alberti Tommaso
  • Antolin Patrick
  • Aznar Cuadrado Regina
  • Berghmans David
  • Brigitte Schmieder
  • Bucik Radoslav
  • Calchetti Daniele
  • Caspi Amir
  • Cohen Christina
  • Corbard Thierry
  • Cremades Hebe
  • Cummings Alan
  • Dhakal Suman
  • Dolla Laurent
  • Dominique Marie
  • Emslie Gordon
  • Ferrente Fabiana
  • Finley Adam J.
  • Fletcher Lyndsay
  • Fraschetti Federico
  • Gafeira Ricardo
  • Gissot Samuel
  • Hegde Dinesha
  • Hu Qiang
  • Innocenti Maria Elena
  • Jin Meng
  • Klein Kristopher
  • Kumar Pankaj
  • Lacatus Daniela
  • Magdalenic Jasmina
  • Mandal Sudip
  • Mandrini Cristina H.
  • Mierla Marilena
  • Miralles Mari Paz
  • Moore Ron
  • Neville Jonathan
  • Niembro Tatiana
  • Nikou Eleni
  • Nindos Alexander
  • Papaioannou Athanasios
  • Rajaguru S. Paul
  • Reville Victor
  • Rochus Pierre
  • Rodriguez Luciano
  • Romoli Marco
  • Shestov Sergei
  • Shi Chen
  • Sorriso-Valvo Luca
  • St. Cyr O. C.
  • Sterling Alphohse
  • Stevens Michael L.
  • Susino Roberto
  • Swisdak Marc
  • Thompson Barbara J.
  • Valliappan Senthamizh Pavai
  • Verbeeck Francis
  • Bothmer Volker
  • Xudong Sun
  • Zhukov Andrei
  • Katsiyannis Thanassis
  • Owen Christopher
  • Karna Nishu
  • Janssens Jan
  • Khomenko Elena
  • Gary Dale
  • Bandyopadhyay Riddhi
  • Chhiber Rohit
  • Tenerani Anna
  • Rouillard Alexis
  • Patsourakos Spiros
  • Anastasiadis Anastasios
  • Bocchialini Karine
  • Moraitis Kostas
  • Rivera Yeimy
  • Drake James
  • Baudin Frédéric
  • Chandran Benjamin
  • Dayeh Maher
  • Reardon Kevin
  • Cairns Iver
  • Bizien Nina
  • Wexler David
  • Bahauddin Shah
  • Rodriguez-Pacheco Javier
  • Yu Sijie
  • Lee Jeongwoo
  • Gontikakis Costis
  • Koukras Alexandros
  • Le Contel Olivier
  • Pezzi Oreste
  • Kintziger Christian
  • Boumier Patrick
  • Balasis Georgios
  • Dikpati Mausumi
  • Pesnell W. Dean
  • Chai Yi
  • Nandy Dibyendu
  • Charles Arge
  • Corti Claudio
  • Zhao Lulu
  • Matthaeus William H.
  • Gilly Chris R.
  • Erlandson Robert E.
  • Derouich Moncef
  • Zhao Lingling
  • Poedts Stefaan
  • Shi Chen
  • Vieira Luis
  • Adhikari Laxman
  • Buitrago-Casas Juan Camilo
  • Huang Jia
  • Moestl Christian
  • Liu Mingzhe
  • Oloketuyi Jacob
  • Zhuang Bin
  • Alberti Tommaso
  • Rodríguez-García Laura
  • Perez Jean Carlos
  • Xu Zigong
  • Kooi Jason
  • Woodham Lloyd D.
  • Tripathi Durgesh
  • Young Peter
  • López-Portela Cynthia
  • Cuesta Manuel Enrique
  • Wilson Lynn
  , 2023, 55. This white paper is on the HMCS Firefly mission concept study. Firefly focuses on the global structure and dynamics of the Sun's interior, the generation of solar magnetic fields, the deciphering of the solar cycle, the conditions leading to the explosive activity, and the structure and dynamics of the corona as it drives the heliosphere. (10.3847/25c2cfeb.c647a83d)
  DOI : 10.3847/25c2cfeb.c647a83d
• Characterization of a DC glow discharge in N₂-H₂ with electrical measurements and neutral and ion mass spectrometry
  
  • Chatain Audrey
  • Morillo-Candas Ana Sofia
  • Vettier Ludovic
  • Carrasco Nathalie
  • Cernogora Guy
  • Guaitella Olivier
  Plasma Sources Science and Technology, IOP Publishing, 2023, 32 (3), pp.035002. The addition of small amounts of H2 were investigated in a DC glow discharge in N2, at low pressure (~1 mbar) and low power (0.05 to 0.2 W.cm-3). We quantified the electric field, the electron density, the ammonia production and the formation of positive ions for amounts of H2 varying between 0 and 5%, pressure values between 0.5 and 4 mbar, and currents between 10 and 40 mA.
The addition of less than 1% H2 has a strong effect on the N2 plasma discharges. Hydrogen quenches the (higher) vibrational levels of N2 and some of its highly energetic metastable states. This leads to the increase of the discharge electric field and consequently of the average electron energy. As a result, higher quantities of radical and excited species are suspected to be produced. The addition of hydrogen also leads to the formation of new species. In particular, ammonia and hydrogen-bearing ions have been observed: N2H+ and NH4+ being the major ones, and also H3+, NH+, NH2+, NH3+, N3H+ and N3H3+.
The comparison to a radiofrequency capacitively coupled plasma (RF CCP) discharge in similar experimental conditions shows that both discharges led to similar observations. The study of N2-H2 discharges in the laboratory in the adequate ionization conditions then gives some insights on which plasma species made of nitrogen and hydrogen could be present in the ionosphere of Titan. Here, we identified some protonated ions, which are reactive species that could participate to the erosion of organic aerosols on Titan. (10.1088/1361-6595/acc132)
  DOI : 10.1088/1361-6595/acc132
• First perihelion of EUI on the Solar Orbiter mission
  
  • Berghmans David
  • Antolin Patrick
  • Auchère Frédéric
  • Aznar Cuadrado Regina
  • Barczynski Krzysztof
  • Chitta Lakshmi Pradeep
  • Gissot Samuel F.
  • Harra Louise Kim
  • Huang Zhenghua
  • Janvier Miho
  • Kraaikamp Emil
  • Long David M.
  • Mandal Sudip
  • Mierla Marilena
  • Parenti Susanna
  • Peter Hardi
  • Rodriguez Luciano
  • Schühle Udo H.
  • Smith Phil J.
  • Solanki Sami K.
  • Stegen Koen
  • Teriaca Luca
  • Verbeeck Cis
  • West Matthew J.
  • Zhukov Andrei N.
  • Appourchaux Thierry P.
  • Aulanier Guillaume
  • Buchlin Eric
  • Delmotte Franck
  • Gilles J. M.
  • Haberreiter Margit
  • Halain Jean Philippe A.
  • Heerlein Klaus
  • Hochedez Jean-François
  • Gyo Manfred
  • Poedts Stefaan
  • Renotte Etienne
  • Rochus Pierre L.P.M.
  Astronomy & Astrophysics - A&A, EDP Sciences, 2023, 675, pp.A110 (19p.). Context. The Extreme Ultraviolet Imager (EUI) on board Solar Orbiter consists of three telescopes: the two High Resolution Imagers, in EUV (HRIEUV) and in Lyman-α (HRILya), and the Full Sun Imager (FSI). Solar Orbiter/EUI started its Nominal Mission Phase on 2021 November 27. Aims. Our aim is to present the EUI images from the largest scales in the extended corona off-limb down to the smallest features at the base of the corona and chromosphere. EUI is therefore a key instrument for the connection science that is at the heart of the Solar Orbiter mission science goals. Methods. The highest resolution on the Sun is achieved when Solar Orbiter passes through the perihelion part of its orbit. On 2022 March 26, Solar Orbiter reached, for the first time, a distance to the Sun close to 0.3 au. No other coronal EUV imager has been this close to the Sun. Results. We review the EUI data sets obtained during the period 2022 March- April, when Solar Orbiter quickly moved from alignment with the Earth (2022 March 6), to perihelion (2022 March 26), to quadrature with the Earth (2022 March 29). We highlight the first observational results in these unique data sets and we report on the in-flight instrument performance. Conclusions. EUI has obtained the highest resolution images ever of the solar corona in the quiet Sun and polar coronal holes. Several active regions were imaged at unprecedented cadences and sequence durations. We identify in this paper a broad range of features that require deeper studies. Both FSI and HRIEUV operated at design specifications, but HRILya suffered from performance issues near perihelion. We conclude by emphasizing the EUI open data policy and encouraging further detailed analysis of the events highlighted in this paper. (10.1051/0004-6361/202245586)
  DOI : 10.1051/0004-6361/202245586
• Wave-number Space Networks in Plasma Turbulence
  
  • Gürcan Ö.
  Reviews of Modern Plasma Physics, Springer Singapore, 2023, 7 (1), pp.20. Turbulence commonly described in Fourier space due to its multi-scale nature can be formulated using wave number space networks where each node represents a wave-vector on a discretized wave-number space grid that are connected to one another through triadic interactions denoted as three body connections. This description that we call wave-number space network formulation, while being very inefficient for numerical implementation as compared for example to a pseudo-spectral formulation of the same equations on a regular grid, provides an alternative perspective and has conceptual advantages, such as the separation of the equations and the nonlinear interactions. The network represents, through its connections, the nonlinear interactions, and can be truncated by dropping nodes, or connections corresponding to considering only certain kinds of wave-numbers or certain kinds of interactions, without modifying the equations themselves. This guarantees that the underlying Hamiltonian structure of the equations remains unchanged, and therefore one has the same conservation laws as the original system. Wave-number space networks can also be reduced by lumping nodes that have some similar characteristics together, in which case a reduction of the equations through some sort of closure becomes necessary, for which some possibilities are discussed. The network formulation can also be used for analysing direct numerical simulations, and may be used for discovering key nodes as well as training models for constructing reduced systems. The goal of this review is to stimulate interest in thinking in terms of networks, while dealing with problems in plasma turbulence Wave-number Space Networks in Plasma Turbulence through a survey of what has been done in this subfield and what is possible for future studies, especially in the context of plasma turbulence. (10.1007/s41614-023-00122-7)
  DOI : 10.1007/s41614-023-00122-7
• Release of Arabidopsis seed dormancy by cold atmospheric plasma relies on cytoplasmic glass transition
  
  • August Jonas
  • Dufour Thierry
  • Bailly Christophe
  Journal of Physics D: Applied Physics, IOP Publishing, 2023, 56 (41), pp.415202. When mature Arabidopsis thaliana seeds are dormant, their germination is prevented in apparently favorable conditions. This primary dormancy can be released during seed dry storage through a process called after-ripening whose duration can last several months. To reduce this delay, cold atmospheric plasmas (CAPs) can be used as sources of reactive oxygen species (ROS) capable of inducing heterogeneous chemical reactions. While CAP are known to stimulate the germination of various seed species, the relationship between CAP treatments and the amorphous solid state of dry seeds remains unexplored. Here, we demonstrate that seed dormancy can be alleviated using a cold plasma of ambient air and that this alleviation can be amplified for seeds with high water-content (typically 30% DW ) or seeds heated at 60 °C during plasma treatment. Differential scanning micro-calorimetry shows that these characteristics control the glassy/rubbery state of the seed cytoplasm. This technique indicates also that a glass transition to the rubbery state strengthens the CAP effects to alleviate seed dormancy. We propose that lower cytoplasmic viscosity can promote the oxidative signaling induced by CAP which, in turn, improves the germination process. (10.1088/1361-6463/ace36e)
  DOI : 10.1088/1361-6463/ace36e
• Changes of Magnetic Energy and Helicity in Solar Active Regions from Major Flares
  
  • Liu Yang
  • Welsch Brian
  • Valori Gherardo
  • K. Georgoulis Manolis
  • Guo Yang
  • Pariat Etienne
  • Park Sung-Hong
  • Thalmann Julia
  The Astrophysical Journal, American Astronomical Society, 2023, 942 (1), pp.27. Magnetic free energy powers solar flares and coronal mass ejections, and the buildup of magnetic helicity might play a role in the development of unstable structures that subsequently erupt. To better understand the roles of energy and helicity in large flares and eruptions, we have characterized the evolution of magnetic energy and helicity associated with 21 X-class flares from 2010 to 2017. Our sample includes both confined and eruptive events, with 6 and 15 in each category, respectively. Using the Helioseismic and Magnetic Imager vector magnetic field observations from several hours before to several hours after each event, we employ (a) the Differential Affine Velocity Estimator for Vector Magnetograms to determine the photospheric fluxes of energy and helicity, and (b) nonlinear force-free field extrapolations to estimate the coronal content of energy and helicity in source-region fields. Using superposed epoch analysis, we find, on average, the following: (1) decreases in both magnetic energy and helicity, in both photospheric fluxes and coronal content, that persist for a few hours after eruptions, but no clear changes, notably in relative helicity, for confined events; (2) significant increases in the twist of photospheric fields in eruptive events, with twist uncertainties too large in confined events to constrain twist changes (and lower overall twist in confined events); and (3) on longer timescales (event time +12 hr), replenishment of free magnetic energy and helicity content to near preevent levels for eruptive events. For eruptive events, magnetic helicity and free energy in coronal models clearly decrease after flares, with the amounts of decrease proportional to each region’s pre-flare content. (10.3847/1538-4357/aca3a6)
  DOI : 10.3847/1538-4357/aca3a6
• Two-dimensional effects on electrostatic instabilities in Hall thrusters. II. Comparison of particle-in-cell simulation results with linear theory dispersion relations
  
  • Petronio Federico
  • Charoy Thomas
  • Alvarez Laguna Alejandro
  • Bourdon Anne
  • Chabert Pascal
  Physics of Plasmas, American Institute of Physics, 2023, 30 (1), pp.012104. In Paper I, we successfully used an external circuit to significantly damp the Breathing Mode (BM) oscillations in 2D particle-in-cell self-consistent simulations of the axial–azimuthal plane of a Hall thruster. We also introduced the two-point power spectral density reconstruction method (PSD2P) used to analyze electrostatic instabilities and generate dispersion diagrams in azimuthal and axial directions, at various times during the BM period. Here, a 3D Dispersion Relation (DR) for electrostatic modes is calculated by linearizing the continuity/momentum fluid equations for electrons and ions. We show that by taking the appropriate limits, this relation can be simplified to derive the DRs of some well-known [Formula: see text] instabilities, such as the electron cyclotron drift instability and its evolution to the Ion Acoustic Wave (IAW), and the Ion Transit-Time Instability (ITTI). The PSD2P diagrams demonstrate the importance of considering the 2D nature of the IAW and ITTI, which have been previously considered to be mono-dimensional (azimuthal and axial, respectively). In particular, we show that the IAW grows near the maximum of the magnetic field and due to its axial components propagates toward both the anode and the cathode (in addition to the well-known azimuthal propagation). The resulting wavefront is, therefore, bent. By analogy to the propagation of acoustic waves in gases, it is proposed that the cause of the IAW wavefront bending is the strong electron temperature gradients in the axial direction. We also show that the ITTI has a strong positive growth rate when a small azimuthal component is present. Finally, we observe that the ITTI significantly affects the discharge current. (10.1063/5.0119255)
  DOI : 10.1063/5.0119255
• Interchange reconnection dynamics in a solar coronal pseudo-streamer
  
  • Pellegrin-Frachon T.
  • Masson S.
  • Pariat Etienne
  • Wyper P F
  • Devore C R
  Astronomy & Astrophysics - A&A, EDP Sciences, 2023, 675, pp.A55. Context. The generation of the slow solar wind remains an open problem in heliophysics. One of the current theories among those aimed at explaining the injection of coronal plasma in the interplanetary medium is based on interchange reconnection. It assumes that the exchange of magnetic connectivity between closed and open fields allows the injection of coronal plasma in the interplanetary medium to travel along the newly reconnected open field. However, the exact mechanism underlying this effect is still poorly understood. Aims. Our objective is to study this scenario in a particular magnetic structure of the solar corona: a pseudo-streamer. This topological structure lies at the interface between open and closed magnetic field and is thought to be involved in the generation of the slow solar wind. Methods. We performed innovative 3D magnetohydrodynamic (MHD) simulations of the solar corona with a pseudo-streamer, using the Adaptively Refined MHD Solver (ARMS). By perturbing the quasi-steady ambient state with a simple photospheric, large-scale velocity flow, we were able to generate a complex dynamics of the open-and-closed boundary of the pseudo-streamer. We studied the evolution of the connectivity of numerous field lines to understand its precise dynamics. Results. We witnessed different scenarios of opening of the magnetic field initially closed under the pseudo-streamer: one-step interchange reconnection dynamics, along with more complex scenarios, including a coupling between pseudo-streamer and helmet streamer, as well as back-and-forth reconnections between open and closed connectivity domains. Finally, our analysis revealed large-scale motions of a newly opened magnetic field high in the corona that may be explained by slipping reconnection. Conclusions. By introducing a new analysis method for the magnetic connectivity evolution based on distinct closed-field domains, this study provides an understanding of the precise dynamics underway during the opening of a closed field, which enables the injection of closed-field, coronal plasma in the interplanetary medium. Further studies shall provide synthetic observations for these diverse outgoing flows, which could be measured by Parker Solar Probe and Solar Orbiter. (10.1051/0004-6361/202245611)
  DOI : 10.1051/0004-6361/202245611
• Observations of Kolmogorov Turbulence in Saturn's Magnetosphere
  
  • Xu S B
  • Huang S Y
  • Sahraoui Fouad
  • Yuan Z G
  • Wu H H
  • Jiang K.
  • Zhang J.
  • Lin R T
  Geophysical Research Letters, American Geophysical Union, 2023, 50 (16), pp.e2023GL105463. The Kolmogorov scaling in the inertial range of scales is a distinct characteristic of fully developed turbulence, and studying it offers valuable insights into the evolution of turbulence. In this work, we perform a statistical survey of the power spectra with the Kolmogorov scaling in Saturn's magnetosphere using Cassini measurements. Two cases study show that both magnetic‐field and electron density spectra exhibit f^−5/3 at the MHD scales. The statistical analysis reveals a wide‐ranging and abundant presence of Kolmogorov spectra throughout magnetosphere, observed across all local times. Interestingly, the occurrence rate of these Kolmogorov‐like events within Saturn's magnetosphere surpasses that observed in the planetary magnetosheath. The measurements of magnetic compressibility for the Kolmogorov‐like events show the dominance of incompressible Alfvénic turbulence (44.64%) with respect to magnetosonic‐like one (6.94%). In addition, the source and evolution of the turbulent fluctuations are further discussed. (10.1029/2023GL105463)
  DOI : 10.1029/2023GL105463