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| Open AccessMagnetosheath jets at Jupiter and across the solar system
Jets have been found in Earth’s magnetosheath for two decades and, more recently, also in Mars. Yet, their universal existence in planetary magnetosheath remains an open question. Here, authors report the presence of anti-sunward and sunward jets at Jupiter and compare them to Earth and Mars.
- Yufei Zhou
- , Savvas Raptis
- & Lan Ma
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Article
| Open AccessObservational evidence of accelerating electron holes and their effects on passing ions
Electron holes with drift speeds comparable to local ion thermal velocity are called slow electron holes. Here, the authors show slow electron holes with non-zero acceleration can cause net velocity change of ions passing through.
- Yue Dong
- , Zhigang Yuan
- & J. L. Burch
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| Open AccessUltra-high-resolution observations of persistent null-point reconnection in the solar corona
Magnetic reconnection is a fundamental energy release mechanism in space and laboratory plasmas. Here, the authors show persistent magnetic null-point reconnection in the solar corona at a scale of about 390 km.
- X. Cheng
- , E. R. Priest
- & S. Parenti
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Article
| Open AccessEquilibrium selection via current sheet relaxation and guide field amplification
Magnetized plasmas display continuous spectra of current-sheet equilibria. How they select a particular equilibrium is not well understood. Now, equilibrium selection in magnetized plasmas is studied by analytical theory, particle-in-cell simulations and spacecraft observations, highlighting the role of current-sheet relaxation processes.
- Young Dae Yoon
- , Deirdre E. Wendel
- & Gunsu S. Yun
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Article
| Open AccessAccurate temperature diagnostics for matter under extreme conditions
Existing methods for temperature estimation of warm dense matter rely on model calculations. Here the authors report a method to extract the temperature of complex materials that is previously only inferred by using model calculations.
- Tobias Dornheim
- , Maximilian Böhme
- & Jan Vorberger
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Article
| Open AccessMicrowave imaging of quasi-periodic pulsations at flare current sheet
Quasi-periodic pulsations (QPPs) are frequently detected in solar and stellar flares, but the underlying physical mechanisms are still to be ascertained. Here, the authors show microwave QPPs during a solar flare originating from quasi-periodic magnetic reconnection at the flare current sheet.
- Yuankun Kou
- , Xin Cheng
- & Mingde Ding
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Article
| Open AccessThe supernova remnant SN 1006 as a Galactic particle accelerator
It is known that cosmic rays could be accelerated by shock waves in supernova (SN) remnants. Here, the authors show that SN 1006 remnant is an efficient source of cosmic rays, providing observational support for the quasi-parallel acceleration mechanism.
- Roberta Giuffrida
- , Marco Miceli
- & Giovanni Peres
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Article
| Open AccessDirect observations of anomalous resistivity and diffusion in collisionless plasma
It is suggested that waves can provide both diffusion and resistivity that can potentially support the reconnection electric field in low-density astrophysical plasmas. Here, the authors show, using direct spacecraft measurements, that the waves contribute to anomalous diffusion but do not contribute to the reconnection electric field.
- D. B. Graham
- , Yu. V. Khotyaintsev
- & K. Dokgo
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| Open AccessDownstream high-speed plasma jet generation as a direct consequence of shock reformation
Several mechanisms exist for formation of jets observed in Earth’s magnetosheath. Here, the authors show evidence of high-speed downstream flows generated at the Earth’s bow shock as a direct consequence of shock reformation, which is different than the proposed mechanisms.
- Savvas Raptis
- , Tomas Karlsson
- & Per-Arne Lindqvist
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Article
| Open AccessMagnetopause ripples going against the flow form azimuthally stationary surface waves
The magnetopause surface waves (SW) that drive global plasma dynamics are thought, like waves on water, to travel with the driving solar wind. Here, the authors show that impulsively-excited SW, with standing structure along the geomagnetic field, are stationary by propagating against this flow.
- M. O. Archer
- , M. D. Hartinger
- & L. Rastaetter
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| Open AccessTopological phases and bulk-edge correspondence of magnetized cold plasmas
Magnetized plasma can be regarded as topological matter. Here the authors identify a necessary and sufficient condition for the existence of topological edge mode and find that cold magnetized plasma has ten topological phases in the plasma frequency, cyclotron frequency and wave-vector space.
- Yichen Fu
- & Hong Qin
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Article
| Open AccessCollisionless relaxation of a disequilibrated current sheet and implications for bifurcated structures
Bifurcated current sheets are a recurring feature in magnetized space plasmas. Here the authors explain the emergence of bifurcated structures by natural redistributions of single-particle orbits during the collisionless relaxation process of a disequilibrated current sheet.
- Young Dae Yoon
- , Gunsu S. Yun
- & James L. Burch
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| Open AccessObservations of pressure anisotropy effects within semi-collisional magnetized plasma bubbles
Magnetic fields can be reorganized by plasma flows and lead to effects such as magnetic reconnection. Here the authors explore the evolution of magnetized-plasma bubbles in a semi-collisional regime and the role of pressure anisotropy in influencing the flow of the laser-produced plasma.
- E. R. Tubman
- , A. S. Joglekar
- & N. C. Woolsey
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Article
| Open AccessMagnetic pumping model for energizing superthermal particles applied to observations of the Earth's bow shock
Energetic particle generation is an important component of a variety of astrophysical systems. Here, the authors show when magnetic pumping is extended to a spatially-varying magnetic flux tube, magnetic trapping of superthermal particles renders pumping an effective energization method for particles moving faster than the speed of the waves.
- E. Lichko
- & J. Egedal
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Article
| Open AccessDemonstration of X-ray Thomson scattering as diagnostics for miscibility in warm dense matter
It is challenging to reliably probe the miscibility behavior of elements in extreme conditions. Here, the authors use X-ray Thomson scattering and compare to the X-ray diffraction method in order to determine mixing of different atomic species in warm dense matter conditions.
- S. Frydrych
- , J. Vorberger
- & D. Kraus
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Article
| Open AccessEvidence of ubiquitous Alfvén pulses transporting energy from the photosphere to the upper chromosphere
Heating of the upper solar atmospheric layers is an open question. Here, the authors show observational evidence that ubiquitous Alfven pulses are excited by prevalent photospheric swirls, which are found to propagate upwards and carry enough energy flux needed to balance the local upper chromospheric energy loss.
- Jiajia Liu
- , Chris J. Nelson
- & Robert Erdélyi
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Article
| Open AccessLoss-cone instability modulation due to a magnetohydrodynamic sausage mode oscillation in the solar corona
Magnetohydrodynamic (MHD) waves and plasma instabilities can be studied during solar flares. Here the authors show evidence for an MHD sausage mode oscillation periodically triggering electron acceleration at a magnetic null point in the solar corona, indicating MHD oscillations in plasma can indirectly lead to loss-cone instability modulation.
- Eoin P. Carley
- , Laura A. Hayes
- & Peter T. Gallagher
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Article
| Open AccessSupersonic plasma turbulence in the laboratory
Supersonic turbulence is relevant to astrophysical plasmas with their study mostly limited to numerical simulations. Here the authors demonstrate supersonic turbulence in collisional high Mach number plasma jets generated in laboratory by using high power lasers.
- T. G. White
- , M. T. Oliver
- & G. Gregori
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Article
| Open AccessEvidence for electron Landau damping in space plasma turbulence
Various physical mechanisms are proposed to explain the heating observed in turbulent astrophysical plasmas. Here, Chen et al. find a signature consistent with one of these mechanisms, electron Landau damping, by applying a field-particle correlation technique to in situ spacecraft data of turbulence in the Earth’s magnetosheath.
- C. H. K. Chen
- , K. G. Klein
- & G. G. Howes
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| Open AccessDirect observations of a surface eigenmode of the dayside magnetopause
Surface waves on the boundary between a magnetosphere and the surrounding plasma might get trapped by the ionosphere forming an eigenmode. Here, Archer et al. show direct observations of this proposed mechanism at Earth’s magnetosphere by analyzing the response to an isolated fast plasma jet detected by the THEMIS satellites.
- M. O. Archer
- , H. Hietala
- & V. Angelopoulos
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| Open AccessThe two-fluid dynamics and energetics of the asymmetric magnetic reconnection in laboratory and space plasmas
Magnetic energy in the plasma is transferred into particle energy by magnetic reconnection. Here the authors show the two-fluid dynamics of asymmetric magnetic reconnection in two different spatial scales of plasma, namely laboratory and astrophysical plasma.
- M. Yamada
- , L.-J. Chen
- & R. Torbert
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| Open AccessMagnetic reconnection driven by electron dynamics
Magnetic reconnection is the process of releasing energy by magnetized and space plasma. Here the authors report experimental observation of magnetic reconnection in laser-produced plasma and the role of electron scaling on reconnection.
- Y. Kuramitsu
- , T. Moritaka
- & M. Hoshino
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Article
| Open AccessFormation of electron radiation belts at Saturn by Z-mode wave acceleration
Radial diffusion is the only mechanism considered to accelerate trapped electrons to relativistic energies in Saturn’s magnetic field, forming radiation belts. Here the authors show another mechanism, electron acceleration via Doppler shifted cyclotron resonant interaction with Z-mode waves, which can form radiation belts inside the orbit of Enceladus.
- E. E. Woodfield
- , R. B. Horne
- & W. S. Kurth
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Article
| Open AccessExplaining the apparent impenetrable barrier to ultra-relativistic electrons in the outer Van Allen belt
The origin of the apparent impenetrable barrier in the outer Van Allen belt is still uncertain. Here, the authors report that penetration to the barrier can occur by means of ultra-low frequency wave transport, enabling ultra-relativistic electrons to reach the location of the barrier.
- Louis G. Ozeke
- , Ian R. Mann
- & Harlan E. Spence
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Article
| Open AccessThe creation of electric wind due to the electrohydrodynamic force
The electric wind mechanism remains unclear. Here, the authors report evidence that electric wind is caused by an electrohydrodynamic force generated by charged particle drag as a result of momentum transfer to neutral particles.
- Sanghoo Park
- , Uros Cvelbar
- & Se Youn Moon
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| Open AccessTurbulent mass transfer caused by vortex induced reconnection in collisionless magnetospheric plasmas
Vortex-induced reconnection originates from non-linear vortex flows due to Kelvin-Helmholtz instability in the Earth’s magnetosphere. Here, the authors perform a large-scale kinetic simulation to unveil dynamics of the vortex-induced reconnection and resulting turbulent mixing process.
- T. K. M. Nakamura
- , H. Hasegawa
- & R. Nakamura
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Article
| Open AccessImaging spectroscopy of solar radio burst fine structures
Radio observations of the solar atmosphere provide a unique view on the non-thermal processes in the outer atmosphere. Here the authors use LOFAR observations to demonstrate that the observed radio burst characteristics are dominated by propagation effects rather than underlying emission variations.
- E. P. Kontar
- , S. Yu
- & P. Subramanian
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Article
| Open AccessBuildup of a highly twisted magnetic flux rope during a solar eruption
Solar eruptions provide opportunities to study magnetic flux ropes, a structure of fundamental importance for both plasma physics and space weather. Here the authors reveal the dynamic formation of a flux rope through its footprint on the solar surface, revealing a highly twisted core structure.
- Wensi Wang
- , Rui Liu
- & Chunming Zhu
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Article
| Open AccessMagnetic turbulence in a table-top laser-plasma relevant to astrophysical scenarios
Understanding the role of magnetic turbulence in the atmosphere is difficult as direct access is limited, but latest laser technology can enable such studies in the lab. Here the authors probe the evolution of such turbulence in laser-generated plasma with its implications to astrophysical environments.
- Gourab Chatterjee
- , Kevin M. Schoeffler
- & G. Ravindra Kumar
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Article
| Open AccessBeam electrons as a source of Hα flare ribbons
The dynamic of plasma heating in solar flares can be effectively derived from observations of optical hydrogen H-α line emissions. Here the authors report the observation of a C1.5 class flare that produced two H-α ribbons, interpreted combining radiative models affected by an electron beam.
- Malcolm Druett
- , Eamon Scullion
- & Luc Rouppe Van der Voort
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| Open AccessWave-particle energy exchange directly observed in a kinetic Alfvén-branch wave
Alfvén waves are fundamental plasma modes that provide a mechanism for the transfer of energy between particles and fields. Here the authors confirm experimentally the conservative energy exchange between Alfvén wave fields and plasma particles via high-resolution MMS observations of Earth’s magnetosphere.
- Daniel J. Gershman
- , Adolfo F-Viñas
- & James L. Burch
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Article
| Open AccessObservation of a reversal of rotation in a sunspot during a solar flare
Back reaction of coronal magnetic fields on the solar surface may help to understand the coronal reconfiguration during a solar flare. Here the authors report observation of reversal of the rotation of a sunspot during a X1.6 flare with data from HMI.
- Yi Bi
- , Yunchun Jiang
- & Zhe Xu
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Article
| Open AccessFlare differentially rotates sunspot on Sun’s surface
Sunspots are concentration of magnetic field visible on the solar surface, which were thought to be unaffected by solar flares that take place in the solar corona. Here the authors report evidence of a flare-induced rotation of a sunspot, showing nonuniform acceleration following the peaks of X-ray emissions.
- Chang Liu
- , Yan Xu
- & Haimin Wang
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Article
| Open AccessScaled laboratory experiments explain the kink behaviour of the Crab Nebula jet
The periodical change of the Crab nebula’s jet direction challenges our understanding of astrophysical jet dynamics. Here the authors use high-power lasers to create a jet that can be directly compared to the Crab nebula’s, and report the detection of plasma instabilities that mimic kink behaviour.
- C. K. Li
- , P. Tzeferacos
- & N. C. Woolsey
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Article
| Open AccessWave-induced loss of ultra-relativistic electrons in the Van Allen radiation belts
The processes that lead to losses of highly energetic particles from Earth’s radiation belts remain poorly understood. Here the authors compare observations and models of a 2013 event to show that electromagnetic ioncyclotron waves provide the dominant loss mechanism at ultra-relativistic energies.
- Yuri Y. Shprits
- , Alexander Y. Drozdov
- & Nikita A. Aseev
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Article
| Open AccessObserving the release of twist by magnetic reconnection in a solar filament eruption
Magnetic reconnection is a fundamental process giving rise to topology change and energy release in plasmas, of particular relevance for the Sun. Here the authors report the observation of fast reconnection in a solar filament eruption, which occurs between a set of ambient fibrils and the filament itself.
- Zhike Xue
- , Xiaoli Yan
- & Li Zhao
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Article
| Open AccessInvestigating Alfvénic wave propagation in coronal open-field regions
Alfvénic waves are oscillations that occur in a plasma threaded by a magnetic field and their propagation, reflection and dissipation is believed to be partly responsible for the solar wind. Here, the authors observe the counter-propagating Alfvénic waves that most models require for solar-wind acceleration.
- R. J. Morton
- , S. Tomczyk
- & R. Pinto
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Article
| Open AccessGeneration of neutral and high-density electron–positron pair plasmas in the laboratory
Electron–positron pair plasma—a state of matter with a complete symmetry between negatively and positively charged particles—are found in many astrophysical object. Here, the authors use high-power laser to create an ion-free electron–positron plasma in the laboratory.
- G. Sarri
- , K. Poder
- & M. Zepf
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Observations of ubiquitous compressive waves in the Sun’s chromosphere
A full understanding of the heating and dynamics of the Sun's atmosphere remains elusive, but magnetohydrodynamic waves are believed to be crucial. Using observations from the ROSA imager, this study finds compressive waves in the solar chromosphere, which may provide the energy needed for coronal heating.
- Richard J. Morton
- , Gary Verth
- & Robertus Erdélyi
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Article
| Open AccessEvidence of superdense aluminium synthesized by ultrafast microexplosion
At extreme temperature and pressure, materials can form new dense phases with unusual physical properties. Here, laser-induced microexplosions are used to produce a superdense, stable, body-centred-cubic form of aluminium, which was previously predicted to exist at pressures above 380GPa.
- Arturas Vailionis
- , Eugene G. Gamaly
- & Saulius Juodkazis
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| Open AccessSize limits the formation of liquid jets during bubble bursting
A bubble at an air–liquid interface can form a liquid jet upon bursting, spraying aerosol droplets into the air. Leeet al. show that jetting is analogous to pinching-off in liquid coalescence, which may be useful in applications that prevent jet formation and in the improved incorporation of aerosols in climate models.
- Ji San Lee
- , Byung Mook Weon
- & Wah-Keat Lee
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Article
| Open AccessFractal fronts of diffusion in microgravity
Theory and simulations predict scale-invariant concentration fluctuations during diffusion in liquids, but on Earth, large-scale fluctuations are damped by gravity. Microgravity experiments by Vailatiet al. reveal the scale-invariant nature of diffusion, associated with fractal fronts and long-ranged correlations.
- Alberto Vailati
- , Roberto Cerbino
- & Marzio Giglio