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| Open AccessNetwork community structure of substorms using SuperMAG magnetometers
During geomagnetic substorms, the energy accumulated from solar wind is abruptly transported to ionosphere. Here, the authors show application of community detection on the time-varying networks constructed from all magnetometers collaborating with the SuperMAG initiative.
- L. Orr
- , S. C. Chapman
- & W. Guo
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Article
| Open AccessA space hurricane over the Earth’s polar ionosphere
Hurricanes in the Earth’s low atmosphere are known, but not detected in the upper atmosphere earlier. Here, the authors show a long-lasting hurricane in the polar ionosphere and magnetosphere with large energy and momentum deposition despite otherwise extremely quiet conditions.
- Qing-He Zhang
- , Yong-Liang Zhang
- & Li-Dong Xia
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Matters Arising
| Open AccessRapid 14C excursion at 3372-3371 BCE not observed at two different locations
- A. J. Timothy Jull
- , Irina P. Panyushkina
- & Willy Tegel
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Article
| Open AccessNorthern preference for terrestrial electromagnetic energy input from space weather
Seasonally averaged energy input into the ionosphere from geospace is generally considered to be symmetric. Here, the authors show preference for electromagnetic energy input at 450 km altitude into the northern hemisphere, on both the dayside and the nightside, when averaged over season.
- I. P. Pakhotin
- , I. R. Mann
- & D. J. Knudsen
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| Open AccessSelf-consistent kinetic model of nested electron- and ion-scale magnetic cavities in space plasmas
Magnetic cavities play important roles in the energy cascade, conversion and dissipation in turbulent plasmas. Here, the authors show a theoretical insight into magnetic cavities by deriving a self-consistent, kinetic theory of these coherent structures.
- Jing-Huan Li
- , Fan Yang
- & James L. Burch
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Article
| Open AccessMagnetotail reconnection onset caused by electron kinetics with a strong external driver
Magnetotail reconnection plays a crucial role in explosive energy conversion in geospace. Here, the authors show that magnetotail reconnection starts from electron reconnection in the presence of a strong external driver, which then develops into ion reconnection.
- San Lu
- , Rongsheng Wang
- & Shui Wang
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Article
| Open AccessA transient enhancement of Mercury’s exosphere at extremely high altitudes inferred from pickup ions
Mercury has a global dayside exosphere that is very tenuous and does not extend far from the planet. Here, the authors show enhancement of neutral densities at high altitudes inferred from pickup ions that is most likely caused by the impact of a meteroid.
- Jamie M. Jasinski
- , Leonardo H. Regoli
- & Neil Murphy
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Article
| Open AccessVery-Low-Frequency transmitters bifurcate energetic electron belt in near-earth space
Very-Low-Frequency (VLF) communication transmitters, operate worldwide, radiate emissions at particular frequencies 10-30 kHz. Here, the authors show VLF transmitter emissions that leak from the Earth’s ground are primarily responsible for bifurcating the energetic electron belt over 20–100 keV.
- Man Hua
- , Wen Li
- & Geoffrey D. Reeves
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Article
| Open AccessLocal heating of radiation belt electrons to ultra-relativistic energies
Electrons in the Van Allen radiation belts can have energies in excess of 7 MeV, however, the energization mechanism is debated. Here, the authors show phase space density peaks in magnetic coordinate space as a way of analyzing satellite observations which demonstrates that local acceleration is capable of heating electrons up to 7 MeV.
- Hayley J. Allison
- & Yuri Y. Shprits
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| Open AccessSolar system exploration via comparative planetology
Knowing about the diversity of planetary processes is of paramount importance for understanding our planet Earth. An integrated, comparative planetology approach is required to combine space missions, autonomous surface exploration, sample return laboratories, and after-mission data exploitation.
- Karl-Heinz Glassmeier
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Article
| Open AccessDirect evidence of secondary reconnection inside filamentary currents of magnetic flux ropes during magnetic reconnection
Magnetic reconnection is a fundamental plasma process of magnetic energy conversion to kinetic energy. Here, the authors show direct evidence of secondary reconnection in the filamentary currents within the flux ropes indicating a significant contribution to energy conversion in the kinetic scale during turbulent reconnection.
- Shimou Wang
- , Rongsheng Wang
- & Shui Wang
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Article
| Open AccessDaylight space debris laser ranging
Space debris laser ranging is a technique to measure distances to defunct satellites or rocket bodies in orbits around Earth which was only possible within a few hours around twilight. Here, the authors show the first space debris laser ranging results during daylight while correcting inaccurate predictions using a real-time target detection software.
- Michael A. Steindorfer
- , Georg Kirchner
- & Tim Flohrer
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Article
| Open AccessDesign and flight results of the VHF/UHF communication system of Longjiang lunar microsatellites
Satellites with amateur radio communication capabilities have not been operated in lunar orbit before. Here, the authors present the design and performance of a VHF/UHF software-defined radio developed for and tested on lunar microsatellites.
- Mingchuan Wei
- , Chaoran Hu
- & Feng Wang
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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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| Open AccessPlasmapause surface wave oscillates the magnetosphere and diffuse aurora
Theoretical studies suggested that plasmapause surface waves related to the sharp inhomogeneity exist and act as a source of geomagnetic pulsations. Here, the authors show direct observations of a plasmapause surface wave and its impacts during a geomagnetic storm using multi-satellite and ground-based observations.
- Fei He
- , Rui-Long Guo
- & Wei-Xing Wan
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Article
| Open AccessElectron Bernstein waves driven by electron crescents near the electron diffusion region
Various types of plasma waves are generated around electron diffusion regions (EDRs). Here the authors show electron Bernstein waves (EBWs), at the electron-scale boundary of the Hall current reversal near EDR, are sufficiently strong to diffuse electrons and modify electron pressure tensor.
- W. Y. Li
- , D. B. Graham
- & J. L. Burch
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Article
| Open AccessOrigin of two-band chorus in the radiation belt of Earth
Chorus waves are crucial on radiation belt dynamics in the space of magnetized planets. Here, the authors show that initially excited single-band chorus waves can quickly accelerate medium energy electrons, and divide the anisotropic electrons into low and high energy components, which subsequently excite two-band chorus waves.
- Jinxing Li
- , Jacob Bortnik
- & Daniel N. Baker
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Article
| Open AccessGigantic jet discharges evolve stepwise through the middle atmosphere
Gigantic jets, lightning discharges originating from tropical thunderstorms that can reach the base of the ionosphere at 90 km altitude, have not been captured using high-speed video cameras before. Here, the first such images are reported, showing a step-wise evolution of gigantic jets during their rising phase.
- Oscar A. van der Velde
- , Joan Montanyà
- & Steven A. Cummer
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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 AccessEvidence for low density holes in Jupiter’s ionosphere
Intense electromagnetic impulses induced by Jupiter’s lightning can produce both low-frequency dispersed whistler emissions and non-dispersed radio pulses. Here, the authors show Jupiter dispersed pulses associated with Jovian lightning that are evidence of low density holes in Jupiter’s ionosphere.
- Masafumi Imai
- , Ivana Kolmašová
- & Steven M. Levin
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| 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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| Open AccessMMS observations of electron scale magnetic cavity embedded in proton scale magnetic cavity
Magnetic cavities are universal phenomena existing in cosmic plasma environments. Here Liu et al. show electron scale magnetic cavities in proton scale magnetic cavities observed by Magnetospheric Multiscale (MMS) spacecraft in the Earth’s magnetosheath, and depict the boundary of the electron scale magnetic cavity using particle sounding technique.
- H. Liu
- , Q.-G. Zong
- & R. Rankin
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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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Article
| Open AccessVisualization of rapid electron precipitation via chorus element wave–particle interactions
Electron precipitation plays major role in magnetospheric physics and space weather. Here the authors show nonlinear behavior of the wave–particle interaction in the magnetosphere as the evolution of chorus electromagnetic waves detected by the Arase satellite and PWING observatory.
- Mitsunori Ozaki
- , Yoshizumi Miyoshi
- & Iku Shinohara
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| Open AccessA metamaterial-enabled design enhancing decades-old short backfire antenna technology for space applications
There is significant interest in providing real-world applications for metamaterials. Here, the authors design an Advanced Short Backfire Antenna, augmented with anisotropic metamaterial surfaces to achieve high aperture efficiency across two frequency bands, making the antenna ideal for spaceborne applications.
- J. Daniel Binion
- , Erik Lier
- & Douglas H. Werner
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Article
| 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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Article
| Open AccessPrediction of the strength and timing of sunspot cycle 25 reveal decadal-scale space environmental conditions
The Sun’s activity cycle impacts space-reliant technologies and the Earth’s climate, but predicting this is challenging. An ensemble forecast based on an innovative combination of two solar magnetic field evolution models indicates a weak, but not insignificant sunspot cycle 25 peaking in 2024.
- Prantika Bhowmik
- & Dibyendu Nandy
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Article
| 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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| Open AccessA diagnosis of the plasma waves responsible for the explosive energy release of substorm onset
The origin of geomagnetic substorms is still uncertain due to lack of comprehensive quantitative analyses. Here, the authors construct an observational dispersion relation of auroral forms that correspond to the explosive energy release from substorm onset.
- N. M. E. Kalmoni
- , I. J. Rae
- & C. Forsyth
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Article
| Open AccessRemote sensing of geomagnetic fields and atomic collisions in the mesosphere
Remote sensing of geomagnetic fields in mesosphere is both challenging and interesting to explore the magnetic field structures and atomic collision processes. Here the authors demonstrate an atomic magnetometer that utilizes the Larmor frequency in sodium atoms and operates in kilometers range.
- Felipe Pedreros Bustos
- , Domenico Bonaccini Calia
- & Simon Rochester
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Article
| Open AccessSounding-rocket microgravity experiments on alumina dust
Alumina is thought to be the main condensate to form in the gas outflow from oxygen-rich evolved stars. Here, the authors perform a condensation experiment with alumina in a low-gravity environment, and find spectroscopic evidence for a sharp feature at a wavelength of 13.55 μm.
- Shinnosuke Ishizuka
- , Yuki Kimura
- & Yuko Inatomi
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Article
| Open AccessSolar superstorm of AD 774 recorded subannually by Arctic tree rings
Tree rings retain information of sudden variations of ancient radiocarbon (14C) content, however the origin and exact timing of these events often remain uncertain. Here, the authors analyze a set of Arctic tree rings and link a rapid increase in 14C to a solar event that occurred during the spring of AD 774.
- J. Uusitalo
- , L. Arppe
- & M. Oinonen
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Article
| Open AccessMajor upwelling and overturning in the mid-latitude F region ionosphere
The ionosphere can give rise to irregularities that can interfere with radio communication, navigation and satellite systems. Here the authors present unique observations from the Arecibo Radio Observatory in Puerto Rico to reveal the existence of plasma irregularities occur in the mid-latitude F-region.
- David Hysell
- , Miguel Larsen
- & Michael Sulzer
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| Open AccessStrong whistler mode waves observed in the vicinity of Jupiter’s moons
Observations of Jupiter’s magnetosphere provide opportunities to understand how magnetic fields interact with particles. Here, the authors report that the chorus wave power is increased in the vicinity of Europa and Ganymede. The generated waves are able to accelerate particles to very high energy.
- Y. Y. Shprits
- , J. D. Menietti
- & D. A. Gurnett
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| 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 AccessObservationally quantified reconnection providing a viable mechanism for active region coronal heating
The solar corona heating mechanism is still subject to debate. Here, the authors report that impulsive reconnection can give rise to an active region corona that is compatible with extreme-ultraviolet observations.
- Kai E. Yang
- , Dana W. Longcope
- & Yang Guo
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Article
| Open AccessSolar system expansion and strong equivalence principle as seen by the NASA MESSENGER mission
The NASA MESSENGER mission collected a rich dataset enabling determination of Mercury’s ephemeris. Here, the authors analyse MESSENGER data obtained over an extended period of time to quantify parameters related to General Relativity.
- Antonio Genova
- , Erwan Mazarico
- & Maria T. Zuber
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Article
| Open AccessFormation and dynamics of a solar eruptive flux tube
Solar eruptions are large explosions occurring in the solar atmosphere. Here, the authors perform magnetohydrodynamic simulations to unveil the dynamics of a solar eruption, and find that these are dominated by nonlinear processes involving flux tube evolution and reconnection.
- Satoshi Inoue
- , Kanya Kusano
- & Jan Skála
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Article
| Open AccessTransient rotation of photospheric vector magnetic fields associated with a solar flare
The violent solar eruptions known as flares are caused by magnetic reconnection. Here, the authors identify a sudden 12°–20° counter clockwise rotation of vector magnetic fields in photosphere, associated with the emissions of moving flare ribbons.
- Yan Xu
- , Wenda Cao
- & Haimin Wang
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Article
| Open AccessIncreased ionization supports growth of aerosols into cloud condensation nuclei
Ions produced by cosmic rays have been thought to influence aerosol and cloud processes by an unknown mechanism. Here the authors show that the mass flux of ions to aerosols enhances their growth significantly, with implications for the formation of cloud condensation nuclei.
- H. Svensmark
- , M. B. Enghoff
- & J. Svensmark
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Article
| Open AccessA circular white-light flare with impulsive and gradual white-light kernels
White-light flares are rare solar events entailing emission in the optical continuum. Here, the authors report a nearly circular white-light flare observed on March 10th 2015 that contains simultaneously both impulsive and gradual white-light kernels.
- Q. Hao
- , K. Yang
- & Z. Li
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Article
| 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 AccessA rapid cosmic-ray increase in BC 3372–3371 from ancient buried tree rings in China
14C can be absorbed by trees as a result of the interaction of cosmic rays produced by high-energy phenomena with the Earth’s atmosphere. Here, the authors observe a rapid increase of 14C in an ancient buried tree from BC 3372 to BC 3371, and suggest that it could originate from a large solar proton event.
- F. Y. Wang
- , H. Yu
- & K. S. Cheng
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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 AccessA Solar cycle correlation of coronal element abundances in Sun-as-a-star observations
The Sun’s elemental composition is a vital part of understanding the processes that transport energy from the interior to the outer atmosphere. Here, the authors show that if the Sun is observed as a star, then the variation of coronal composition is highly correlated with the F10.7cm radio flux.
- David H. Brooks
- , Deborah Baker
- & Harry P. Warren
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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