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Journal articleChen L-J, Halekas J, Wang S, et al., 2022,
Solitary Magnetic Structures Developed From Gyro-Resonance With Solar Wind Ions at Mars and Earth
, GEOPHYSICAL RESEARCH LETTERS, Vol: 49, ISSN: 0094-8276- Author Web Link
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- Citations: 2
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Journal articleTinoco-Arenas A, Kajdic P, Preisser L, et al., 2022,
Parametric Study of Magnetosheath Jets in 2D Local Hybrid Simulations
, FRONTIERS IN ASTRONOMY AND SPACE SCIENCES, Vol: 9, ISSN: 2296-987X- Author Web Link
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- Citations: 3
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Journal articleMozer FS, Bale SD, Kellogg PJ, et al., 2022,
An Improved Technique for Measuring Plasma Density to High Frequencies on the Parker Solar Probe
, ASTROPHYSICAL JOURNAL, Vol: 926, ISSN: 0004-637X- Author Web Link
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- Citations: 1
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Journal articleRodriguez L, Barnes D, Hosteaux S, et al., 2022,
Comparing the heliospheric cataloging, analysis, and techniques service (HELCATS) manual and automatic catalogues of coronal mass ejections using solar terrestrial relations observatory/heliospheric Imager (STEREO/HI) Data
, Solar Physics: a journal for solar and solar-stellar research and the study of solar terrestrial physics, Vol: 297, ISSN: 0038-0938We present the results of a comparative study between automatic and manually compiled coronal mass ejection (CME) catalogues based on observations from the Heliospheric Imagers (HIs) onboard NASA’s Solar Terrestrial Relations Observatory (STEREO) spacecraft. Using the Computer Aided CME Tracking software (CACTus), CMEs are identified in HI data using an automatic feature-detection algorithm, while the Heliospheric Imagers Catalogue (HICAT) includes CMEs that are detected by visual inspection of HI images. Both catalogues were compiled as part of the EU FP7 Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS) project (www.helcats-fp7.eu). We compare observational parameters of the CMEs from CACTus to those listed in HICAT, such as CME frequency, position angle (PA), and PA-width. We also compare CACTus-derived speeds to speeds derived from applying geometric modelling to the majority of the HICAT CMEs, the results of which are listed in the HELCATS Heliospheric Imagers Geometric Catalogue (HIGeoCAT). We find that both CACTus and HICAT catalogues contain a similar number of events when we exclude events narrower than 20∘, which are not included in the HICAT catalogue but are found to be identified by CACTus. PA-distributions are strongly peaked around 90∘ and 270∘, with a slightly larger CME frequency northwards of the equatorial plane (particularly for the STEREO-A versions of both catalogues). The CME PA-widths in both HICAT and CACTus catalogues peak at approximately 60∘. Manually derived speeds from HIGeoCAT and automatically derived speeds by CACTus correlate well for values lower than 1000 km s−1, in particular when CMEs are propagating close to the plane of the sky.
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Journal articleShi C, Zhao J, Malaspina DM, et al., 2022,
Multiband Electrostatic Waves below and above the Electron Cyclotron Frequency in the Near-Sun Solar Wind
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 926, ISSN: 2041-8205- Author Web Link
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- Citations: 4
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Journal articleVasko IY, Alimov K, Phan T, et al., 2022,
Kinetic-scale Current Sheets in the Solar Wind at 1 au: Scale-dependent Properties and Critical Current Density
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 926, ISSN: 2041-8205- Author Web Link
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- Citations: 9
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Journal articleZank GP, Zhao L-L, Adhikari L, et al., 2022,
Turbulence in the Sub-Alfvenic Solar Wind
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 926, ISSN: 2041-8205- Author Web Link
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- Citations: 26
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Journal articleMostafavi P, Allen RC, McManus MD, et al., 2022,
Alpha-Proton Differential Flow of the Young Solar Wind: Parker Solar Probe Observations
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 926, ISSN: 2041-8205- Author Web Link
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- Citations: 6
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Journal articlevan der Holst B, Huang J, Sachdeva N, et al., 2022,
Improving the Alfven Wave Solar Atmosphere Model Based on Parker Solar Probe Data
, ASTROPHYSICAL JOURNAL, Vol: 925, ISSN: 0004-637X- Author Web Link
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- Citations: 12
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Journal articleBandyopadhyay R, Matthaeus WH, McComas DJ, et al., 2022,
Sub-Alfvenic Solar Wind Observed by the Parker Solar Probe: Characterization of Turbulence, Anisotropy, Intermittency, and Switchback
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 926, ISSN: 2041-8205- Author Web Link
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- Citations: 21
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Journal articleGetachew T, McComas DJ, Joyce CJ, et al., 2022,
PSP/IS⊙IS Observation of a Solar Energetic Particle Event Associated with a Streamer Blowout Coronal Mass Ejection during Encounter 6
, ASTROPHYSICAL JOURNAL, Vol: 925, ISSN: 0004-637X- Author Web Link
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- Citations: 2
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Journal articleArcher M, Southwood D, Hartinger M, et al., 2022,
How a realistic magnetosphere alters the polarizations of surface, fast magnetosonic, and Alfvén waves
, Journal of Geophysical Research: Space Physics, Vol: 127, ISSN: 2169-9380System-scale magnetohydrodynamic (MHD) waves within Earth's magnetosphere are often understood theoretically using box models. While these have been highly instructive in understanding many fundamental features of the various wave modes present, they neglect the complexities of geospace such as the inhomogeneities and curvilinear geometries present. Here, we show global MHD simulations of resonant waves impulsively excited by a solar wind pressure pulse. Although many aspects of the surface, fast magnetosonic (cavity/waveguide), and Alfvén modes present agree with the box and axially symmetric dipole models, we find some predictions for large-scale waves are significantly altered in a realistic magnetosphere. The radial ordering of fast mode turning points and Alfvén resonant locations may be reversed even with monotonic wave speeds. Additional nodes along field lines that are not present in the displacement/velocity occur in both the perpendicular and compressional components of the magnetic field. Close to the magnetopause, the perpendicular oscillations of the magnetic field have the opposite handedness to the velocity. Finally, widely used detection techniques for standing waves, both across and along the field, can fail to identify their presence. We explain how all these features arise from the MHD equations when accounting for a non-uniform background field and propose modified methods that might be applied to spacecraft observations.
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Journal articleAgapitov V, Drake JF, Swisdak M, et al., 2022,
Flux Rope Merging and the Structure of Switchbacks in the Solar Wind
, ASTROPHYSICAL JOURNAL, Vol: 925, ISSN: 0004-637X- Author Web Link
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- Citations: 9
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Journal articleLario D, Richardson IG, Wilson III LB, et al., 2022,
The Extended Field-aligned Suprathermal Proton Beam and Long-lasting Trapped Energetic Particle Population Observed Upstream of a Transient Interplanetary Shock
, ASTROPHYSICAL JOURNAL, Vol: 925, ISSN: 0004-637X- Author Web Link
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- Citations: 2
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Journal articleShebanits O, Wahlund J-E, Waite JH, et al., 2022,
Conductivities of Titan's Dusty Ionosphere
, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 127, ISSN: 2169-9380- Author Web Link
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- Citations: 1
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Journal articleSimon Wedlund CL, Volwerk M, Beth A, et al., 2021,
A fast bow shock location predictor-estimator from 2D and 3D analytical models: Application to Mars and the MAVEN mission
, Journal of Geophysical Research: Space Physics, ISSN: 2169-9380 -
Journal articleArcher M, Waters C, Dewan S, et al., 2022,
GC Insights: Space sector careers resources need a greater diversity of roles
<jats:p>Abstract. Educational research highlights that improved careers education is needed to increase participation in STEM. Current careers resources concerning the space sector, however, are found to perhaps not best reflect the diversity of roles present and may in fact perpetuate misconceptions about the usefulness of science. We, therefore, compile a more diverse set of space-related jobs, which will be used in the development of a new space careers resource. </jats:p>
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Journal articleChristensen MW, Gettelman A, Cermak J, et al., 2022,
Opportunistic experiments to constrain aerosol effective radiative forcing
, Atmospheric Chemistry and Physics, Vol: 22, Pages: 641-674, ISSN: 1680-7316Aerosol–cloud interactions (ACIs) are considered to be the most uncertain driver of present-day radiative forcing due to human activities. The nonlinearity of cloud-state changes to aerosol perturbations make it challenging to attribute causality in observed relationships of aerosol radiative forcing. Using correlations to infer causality can be challenging when meteorological variability also drives both aerosol and cloud changes independently. Natural and anthropogenic aerosol perturbations from well-defined sources provide “opportunistic experiments” (also known as natural experiments) to investigate ACI in cases where causality may be more confidently inferred. These perturbations cover a wide range of locations and spatiotemporal scales, including point sources such as volcanic eruptions or industrial sources, plumes from biomass burning or forest fires, and tracks from individual ships or shipping corridors. We review the different experimental conditions and conduct a synthesis of the available satellite datasets and field campaigns to place these opportunistic experiments on a common footing, facilitating new insights and a clearer understanding of key uncertainties in aerosol radiative forcing. Cloud albedo perturbations are strongly sensitive to background meteorological conditions. Strong liquid water path increases due to aerosol perturbations are largely ruled out by averaging across experiments. Opportunistic experiments have significantly improved process-level understanding of ACI, but it remains unclear how reliably the relationships found can be scaled to the global level, thus demonstrating a need for deeper investigation in order to improve assessments of aerosol radiative forcing and climate change.
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Journal articleChadney JM, Koskinen TT, Hu X, et al., 2022,
Energy deposition in Saturn's equatorial upper atmosphere
, Icarus, Vol: 372, Pages: 1-16, ISSN: 0019-1035We construct Saturn equatorial neutral temperature and density profiles of H, H2, He, and CH4, between 10−12 and 1 bar using measurements from Cassini’s Ion Neutral Mass Spectrometer (INMS) taken during the spacecraft’s final plunge into Saturn’s atmosphere on 15 September 2017, combined with previous deeper atmospheric measurements from the Cassini Composite InfraRed Spectrometer (CIRS) and from the UltraViolet Imaging Spectrograph (UVIS). These neutral profiles are fed into an energy deposition model employing soft X-ray and Extreme UltraViolet (EUV) solar fluxes at a range of spectral resolutions (∆λ = 4×10−3 nm to 1 nm) assembled from TIMED/SEE, from SOHO/SUMER, and from the Whole Heliosphere Interval (WHI) quiet Sun campaign. Our energy deposition model calculates ion production rate profiles through photo-ionisation and electron-impact ionisation processes, as well as rates of photo-dissociation of CH4. The ion reaction rate profiles we determine are important to obtain accurate ion density profiles, meanwhile methane photo-dissociation is key to initiate complex organic chemical processes. We assess the importance of spectral resolution in the energy deposition model by using a high-resolution H2 photo-absorption cross section, which has the effect of producing additional ionisation peaks near 800 km altitude. We find that these peaks are still formed when using low resolution (∆λ = 1 nm) or mid-resolution (∆λ = 0.1 nm) solar spectra, as long as high-resolution cross sections are included in the model.
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Journal articleStawarz J, Eastwood J, Phan T, et al., 2022,
Turbulence-driven magnetic reconnection and the magnetic correlation length: observations from magnetospheric multiscale in Earth's magnetosheath
, Physics of Plasmas, Vol: 29, Pages: 1-20, ISSN: 1070-664XTurbulent plasmas generate a multitude of thin current structures that can be sites for magnetic reconnection. The Magnetospheric Multiscale (MMS) mission has recently enabled the detailed examination of such turbulent current structures in Earth's magnetosheath and revealed that a novel type of reconnection, known as electron-only reconnection, can occur. In electron-only reconnection, ions do not have enough space to couple to the newly reconnected magnetic fields, suppressing ion jet formation and resulting in thinner sub-proton-scale current structures with faster super-Alfvénic electron jets. In this study, MMS observations are used to examine how the magnetic correlation length (λC) of the turbulence, which characterizes the size of the large-scale magnetic structures and constrains the length of the current sheets formed, influences the nature of turbulence-driven reconnection. We systematically identify 256 reconnection events across 60 intervals of magnetosheath turbulence. Most events do not appear to have ion jets; however, 18 events are identified with ion jets that are at least partially coupled to the reconnected magnetic field. The current sheet thickness and electron jet speed have a weak anti-correlation, with faster electron jets at thinner current sheets. When 𝜆𝐶≲20 ion inertial lengths, as is typical near the sub-solar magnetosheath, a tendency for thinner current sheets and potentially faster electron jets is present. The results are consistent with electron-only reconnection being more prevalent for turbulent plasmas with relatively short λC and may be relevant to the nonlinear dynamics and energy dissipation in turbulent plasmas.
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Conference paperAngelini V, O'Brien H, Horbury T, et al., 2022,
Novel magnetic cleaning techniques for Solar Orbiter magnetometer
Solar Orbiter is an ESA mission studying the heliosphere and the Sun. The magnetometer is designed to measure the magnetic field local to the spacecraft and is composed of two sensors located on a boom at different displacement from the spacecraft. This configuration reduces the electromagnetic interference caused by other on-board electrical systems and allows the exploitation of the 'gradiometer technique' to separate spacecraft generated signals from the solar magnetic field. This paper describes the analysis of the magnetometer data to develop a completely novel procedure for removing the magnetic field generated by the spacecraft-controlled heaters, the instruments, and the thrusters on the spacecraft. The difference between the data measured by the two sensors is used to identify this signal, which is then appropriately scaled and removed from the data. This approach produces cleaned magnetic field data which is routinely uploaded to the Solar Orbiter Archive for science exploitation.
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Conference paperEckersley S, Rowe S, Antoniou N, et al., 2022,
A Distributed Space-Weather Sensor System using Small Satellites
, ISSN: 0074-1795Space weather is becoming increasingly important for space and terrestrial activities and is likely to transition to an operational service. Small satellites are ideally suited for space-weather measurements given the need for making simultaneous measurements across both small and large volumes of space. The “Nanosatellites for D3S” Phase 0/A study for ESA was initiated in early 2021 with the objective to assess the feasibility of using nanosatellites for future operational space weather monitoring missions in near-Earth space as part of ESA's Distributed Space Weather Sensor System (D3S) - which itself forms part of the wider ESA Enhanced Space Weather Monitoring System. The study team consortium is highly experienced including sub-contractors supporting SSTL from MSSL, Imperial College London, and VZLU. Surrey Space Centre and Northumbria University are also providing expert consultancy. In the first part of the Phase 0 study, a survey of the measurement requirements and potential space weather instruments was carried out, alongside an investigation into recent relevant nanosatellite missions and future nanosatellite technologies. This was followed by an analysis and trade-off of high level mission architecture concepts eventually converging down to two of the most promising mission architecture concepts, which were further analysed in the latter half of the Phase 0 study. The objective of the first Phase 0 mission architecture concept was to provide near-real time measurements of radiation, thermal plasma and Ionospheric neutrals/plasma, via a constellation of 20x SSTL-21 satellites, in a single LEO orbital plane. The objective of the second Phase 0 mission architecture concept was to provide near-real time measurements of radiation, the Ionosphere and the Thermosphere, via a constellation of 6x 16U SSTL-Cube satellites, in a single LEO orbital plane. The orbit selected for both missions was a 500-600km Sun-Synchronous LEO Orbit with an LTAN of 10:30a
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Journal articleVerniero JL, Chandran BDG, Larson DE, et al., 2022,
Strong Perpendicular Velocity-space Diffusion in Proton Beams Observed by Parker Solar Probe
, ASTROPHYSICAL JOURNAL, Vol: 924, ISSN: 0004-637X- Author Web Link
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- Citations: 9
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Journal articleMalaspina DM, Stenborg G, Mehoke D, et al., 2022,
Clouds of Spacecraft Debris Liberated by Hypervelocity Dust Impacts on Parker Solar Probe
, ASTROPHYSICAL JOURNAL, Vol: 925, ISSN: 0004-637X- Author Web Link
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- Citations: 6
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Journal articleCattell C, Breneman A, Dombeck J, et al., 2022,
Parker Solar Probe Evidence for the Absence of Whistlers Close to the Sun to Scatter Strahl and to Regulate Heat Flux
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 924, ISSN: 2041-8205- Author Web Link
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- Citations: 17
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Journal articleMoestl C, Weiss AJ, Reiss MA, et al., 2022,
Multipoint Interplanetary Coronal Mass Ejections Observed with Solar Orbiter, BepiColombo, Parker Solar Probe, Wind, and STEREO-A
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 924, ISSN: 2041-8205- Author Web Link
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- Citations: 18
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Journal articleBlasl KA, Nakamura TKM, Plaschke F, et al., 2022,
Multi-scale observations of the magnetopause Kelvin-Helmholtz waves during southward IMF
, PHYSICS OF PLASMAS, Vol: 29, ISSN: 1070-664X- Author Web Link
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- Citations: 9
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Journal articleLavergne A, Hemming D, Prentice IC, et al., 2022,
Global decadal variability of plant carbon isotope discrimination and its link to gross primary production.
, Global Change Biology, Vol: 28, Pages: 524-541, ISSN: 1354-1013Carbon isotope discrimination (Δ13C) in C3 woody plants is a key variable for the study of photosynthesis. Yet how Δ13C varies at decadal scales, and across regions, and how it is related to gross primary production (GPP), are still incompletely understood. Here we address these questions by implementing a new Δ13C modelling capability in the land-surface model JULES incorporating both photorespiratory and mesophyll-conductance fractionations. We test the ability of four leaf-internal CO2 concentration models embedded in JULES to reproduce leaf and tree-ring (TR) carbon isotopic data. We show that all the tested models tend to overestimate average Δ13C values, and to underestimate interannual variability in Δ13C. This is likely because they ignore the effects of soil water stress on stomatal behavior. Variations in post-photosynthetic isotopic fractionations across species, sites and years, may also partly explain the discrepancies between predicted and TR-derived Δ13C values. Nonetheless, the “least-cost” (Prentice) model shows the lowest biases with the isotopic measurements, and lead to improved predictions of canopy-level carbon and water fluxes. Overall, modelled Δ13C trends vary strongly between regions during the recent (1979–2016) historical period but stay nearly constant when averaged over the globe. Photorespiratory and mesophyll effects modulate the simulated global Δ13C trend by 0.0015 ± 0.005‰ and –0.0006 ± 0.001‰ ppm−1, respectively. These predictions contrast with previous findings based on atmospheric carbon isotope measurements. Predicted Δ13C and GPP tend to be negatively correlated in wet-humid and cold regions, and in tropical African forests, but positively related elsewhere. The negative correlation between Δ13C and GPP is partly due to the strong dominant influences of temperature on GPP and vapor pressure deficit on Δ13
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Journal articleNakamura TKM, Blasl KA, Hasegawa H, et al., 2022,
Multi-scale evolution of Kelvin–Helmholtz waves at the earth's magnetopause during southward IMF periods
, Physics of Plasmas, Vol: 29, Pages: 012901-012901, ISSN: 1070-664XAt the Earth's low-latitude magnetopause, the Kelvin–Helmholtz instability (KHI), driven by the velocity shear between the magnetosheath and magnetosphere, has been frequently observed during northward interplanetary magnetic field (IMF) periods. However, the signatures of the KHI have been much less frequently observed during southward IMF periods, and how the KHI develops under southward IMF has been less explored. Here, we performed a series of realistic 2D and 3D fully kinetic simulations of a KH wave event observed by the Magnetospheric Multiscale (MMS) mission at the dusk-flank magnetopause during southward IMF on September 23, 2017. The simulations demonstrate that the primary KHI bends the magnetopause current layer and excites the Rayleigh–Taylor instability (RTI), leading to penetration of high-density arms into the magnetospheric side. This arm penetration disturbs the structures of the vortex layer and produces intermittent and irregular variations of the surface waves which significantly reduces the observational probability of the periodic KH waves. The simulations further demonstrate that in the non-linear growth phase of the primary KHI, the lower-hybrid drift instability (LHDI) is induced near the edge of the primary vortices and contributes to an efficient plasma mixing across the magnetopause. The signatures of the large-scale surface waves by the KHI/RTI and the small-scale fluctuations by the LHDI are reasonably consistent with the MMS observations. These results indicate that the multi-scale evolution of the magnetopause KH waves and the resulting plasma transport and mixing as seen in the simulations may occur during southward IMF
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Journal articleJankee P, Oyedokun D, Soltanian M, et al., 2022,
Geomagnetically Induced Currents: Frequency Spectra and Threats to Voltage Stability
, IEEE ACCESS, Vol: 10, Pages: 62484-62501, ISSN: 2169-3536- Author Web Link
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- Citations: 1
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