Space physics

  • Article
    | Open Access

    Metastable helium is a promising target for remote-sensing observations of Earth’s thermosphere. This paper reports on the development of a resonance lidar capable of resolving metastable helium density profiles and presents initial results

    • Bernd Kaifler
    • , Christopher Geach
    •  & Markus Rapp
  • Article
    | Open Access

    Cross-scale energy transfers in collisionless plasmas help understanding involved mechanisms. Here, the authors show simultaneous macro- and micro-scale wave-ion interactions provide an efficient mechanism for cross-scale energy transfer and plasma energization in astrophysical and space plasmas.

    • Z.-Y. Liu
    • , Q.-G. Zong
    •  & G. Le
  • Article
    | Open Access

    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
  • Article
    | Open Access

    Energetic electron densities in the radiation belt increases during geomagnetic storms. Here, the authors show oblique whistler mode waves enhance electron losses and create strong fluxes of about 100 keV electrons precipitating into the atmosphere, that should be considered in radiation belt models.

    • Xiao-Jia Zhang
    • , Anton Artemyev
    •  & Ayako Matsuoka
  • Article
    | Open Access

    Two extreme solar energetic particle events have been found by carbon isotopes measured in ancient tree rings in 7176 and 5259 BCE. The recorded ~2% increases of atmospheric 14 C for both events exceeds in amplitude of all previously observed events.

    • Nicolas Brehm
    • , Marcus Christl
    •  & Lukas Wacker
  • Article
    | Open Access

    Ring currents have been observed in the magnetospheres of Earth, Jupiter, and Saturn. Here, the authors show observational evidence of Mercury’s ring current that is bifurcated because of the dayside off-equatorial magnetic minima.

    • J.-T. Zhao
    • , Q.-G. Zong
    •  & Y. Wei
  • Article
    | Open Access

    Solar flares provide wide range of observational details about fundamental processes involved. Here, the authors show evidence for magnetic reconnection in a strong confined solar flare displaying all four reconnection flows with plasmoids in the current sheet and the separatrices.

    • Xiaoli Yan
    • , Zhike Xue
    •  & Zhong Liu
  • Article
    | Open Access

    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
  • Article
    | Open Access

    Co-existence of several magnetohydrodynamic oscillations modes on the Sun were predicted earlier. Here, the authors show large-scale coherent oscillations in a sunspot, with a spectrum different than solar global acoustic oscillations, incorporating a superposition of many resonant wave modes.

    • M. Stangalini
    • , G. Verth
    •  & C. D. MacBride
  • Article
    | Open Access

    Twisted flux tubes are prominent candidates for the progenitors of solar active regions. Here, the authors show a clear signature of the emergence of pre-twisted magnetic flux tubes using magnetic winding, which detects the emerging magnetic topology despite the deformation experienced by the emerging magnetic field.

    • D. MacTaggart
    • , C. Prior
    •  & S. L. Guglielmino
  • Article
    | Open Access

    Nonlinear wave mixing has been explored in space plasma. Here the authors report beat-wave Brillouin scattering experiment at EISCAT, in which two radio waves at different transmitted frequencies are driving ion acoustic waves in the ionosphere, leading to stimulated Brillouin emissions escaping the plasma.

    • B. Eliasson
    • , A. Senior
    •  & R. Bingham
  • Article
    | Open Access

    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
  • Article
    | Open Access

    Superbolts are powerful, rare lightning events. Here, the authors show simultaneous satellite and ground measurements of a superbolt, and demonstrate different properties of superbolts and lightnings.

    • J.-F. Ripoll
    • , T. Farges
    •  & S. Pédeboy
  • Article
    | Open Access

    It was predicted that Alfvén waves can account for the acceleration of precipitating auroral electrons. Here, the authors show laboratory measurements of the resonant transfer of energy from Alfvén waves to electrons under conditions relevant to the auroral zone as a direct test.

    • J. W. R. Schroeder
    • , G. G. Howes
    •  & S. Dorfman
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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