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Journal articleWalach M-T, Soobiah Y, Carter JA, et al., 2024,
SMILE winter campaign
, RAS Techniques and Instruments, Vol: 3, Pages: 556-564, ISSN: 2752-8200This white paper is highly topical as it relates to the upcoming solar wind magnetosphere ionosphere link explorer (SMILE) mission: SMILE is a joint mission between the European Space Agency and the Chinese Academy of Sciences and it aims to build a more complete understanding of the Sun–Earth connection by measuring the solar wind and its dynamic interaction with the magnetosphere. It is a fully funded mission with a projected launch in 2025. This paper outlines a plan for action for SMILE’s first Northern hemisphere winter campaign using ground-based instruments. We outline open questions and which data and techniques can be employed to answer them. The science themes we discuss are: (i) Earth’s magnetosheath, magnetopause, and magnetic cusp impact on the ionospheric cusp region; (ii) defining the relationship between auroral processes, solar wind, and magnetospheric drivers; (iii) understanding the interhemispheric properties of the Earth’s magnetosphere–ionosphere system. We discuss open questions (different to the mission goals) which may be answered using existing ground-based instrumentation together with SMILE data to leverage the maximum scientific return of the mission during the first winter after launch. This paper acts as a resource for planning, and a call to collaborative action for the scientific community.
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Journal articleHosner M, Nakamura R, Schmid D, et al., 2024,
Reconnection inside a Dipolarization Front of a diverging Earthward fast flow
, JGR: Space Physics, Vol: 129, ISSN: 2169-9402We examine a Dipolarization Front (DF) event with an embedded electron diffusion region (EDR), observed by the Magnetospheric Multiscale (MMS) spacecraft on 08 September 2018 at 14:51:30 UT in the Earth's magnetotail by applying multi-scale multipoint analysis methods. In order to study the large-scale context of this DF, we use conjunction observations of the Cluster spacecraft together with MMS. A polynomial magnetic field reconstruction technique is applied to MMS data to characterize the embedded electron current sheet including its velocity and the X-line exhaust opening angle. Our results show that the MMS and Cluster spacecraft were located in two counter-rotating vortex flows, and such flows may distort a flux tube in a way that the local magnetic shear angle is increased and localized magnetic reconnection may be triggered. Using multi-point data from MMS we further show that the local normalized reconnection rate is in the range of R ∼ 0.16 to 0.18. We find a highly asymmetric electron in- and outflow structure, consistent with previous simulations on strong guide-field reconnection events. This study shows that magnetic reconnection may not only take place at large-scale stable magnetopause or magnetotail current sheets but also in transient localized current sheets, produced as a consequence of the interaction between the fast Earthward flows and the Earth's dipole field.
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Journal articleSmith AW, Rae IJ, Stawarz JE, et al., 2024,
Automatic Encoding of Unlabeled Two Dimensional Data Enabling Similarity Searches: Electron Diffusion Regions and Auroral Arcs
, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 129, ISSN: 2169-9380 -
Journal articleTosi F, Roatsch T, Galli A, et al., 2024,
Characterization of the Surfaces and Near-Surface Atmospheres of Ganymede, Europa and Callisto by JUICE.
, Space Sci Rev, Vol: 220, ISSN: 0038-6308We present the state of the art on the study of surfaces and tenuous atmospheres of the icy Galilean satellites Ganymede, Europa and Callisto, from past and ongoing space exploration conducted with several spacecraft to recent telescopic observations, and we show how the ESA JUICE mission plans to explore these surfaces and atmospheres in detail with its scientific payload. The surface geology of the moons is the main evidence of their evolution and reflects the internal heating provided by tidal interactions. Surface composition is the result of endogenous and exogenous processes, with the former providing valuable information about the potential composition of shallow subsurface liquid pockets, possibly connected to deeper oceans. Finally, the icy Galilean moons have tenuous atmospheres that arise from charged particle sputtering affecting their surfaces. In the case of Europa, plumes of water vapour have also been reported, whose phenomenology at present is poorly understood and requires future close exploration. In the three main sections of the article, we discuss these topics, highlighting the key scientific objectives and investigations to be achieved by JUICE. Based on a recent predicted trajectory, we also show potential coverage maps and other examples of reference measurements. The scientific discussion and observation planning presented here are the outcome of the JUICE Working Group 2 (WG2): "Surfaces and Near-surface Exospheres of the Satellites, dust and rings".
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Journal articleQuilelli Correa Rocha Ribeiro R, Gryspeerdt E, van Reeuwijk M, 2023,
Retrieving cloud sensitivity to aerosol using ship emissions in overcast conditions
, Geophysical Research Letters, Vol: 50, ISSN: 0094-8276The interaction between aerosols and clouds is one of the major uncertainties in past climate change, affecting the accuracy of future climate projections. Ship tracks, trails left in clouds through the addition of aerosol in the ship exhaust plume, have become a key observational tool for constraining aerosol-cloud interactions. However, manyexpected tracks remain undetected, presenting a significant gap in current knowledge of aerosol forcing. Here we leverage a plume-parcel model to simulate the impact of aerosol dispersion for 2957 cases off California’s coast on cloud droplet number concentration (CDNC) enhancements. Plume-parcel models show a large sensitivity to updraft uncertainties, which are found to be a primary control on track formation. Using these plume-parcel models, updraft values consistent with observed CDNC enhancements are recovered, suggesting that relying solely on cloud-top radiative cooling may overestimate in-cloud updrafts by around 50%, hence overstating the cloud sensitivity to aerosols.
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Journal articleLaker R, Horbury TS, Woodham LD, et al., 2023,
Coherent deflection pattern and associated temperature enhancements in the near-Sun solar wind
, MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 527, Pages: 10440-10447, ISSN: 0035-8711 -
Journal articleSishtla CP, Jebaraj IC, Pomoell J, et al., 2023,
The Effect of the Parametric Decay Instability on the Morphology of Coronal Type III Radio Bursts
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 959, ISSN: 2041-8205 -
Journal articleWilson III LB, Stevens ML, Kasper JC, et al., 2023,
The Statistical Properties of Solar Wind Temperature Parameters Near 1 au (vol 236, 41, 2018)
, ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, Vol: 269, ISSN: 0067-0049 -
Journal articleRasca AP, Farrell WM, Gruesbeck JR, et al., 2023,
Switchbacks and Associated Magnetic Holes Observed near the Alfvén Critical Surface
, ASTROPHYSICAL JOURNAL, Vol: 959, ISSN: 0004-637X -
Journal articleClear CP, Pickering JC, Nave G, et al., 2023,
Wavelengths and Energy Levels of the Upper Levels of Singly Ionized Nickel (Ni <sc>ii</sc>) from 3<i>d</i> <SUP>8</SUP>(<SUP>3</SUP> <i>F</i>)5<i>f</i> to 3<i>d</i> <SUP>8</SUP>(<SUP>3</SUP> <i>F</i>)9<i>s</i>
, ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, Vol: 269, ISSN: 0067-0049 -
Journal articleGiacalone J, Cohen CMS, Mccomas DJ, et al., 2023,
Analyses of ∼0.05-2 MeV Ions Associated with the 2022 February 16 Energetic Storm Particle Event Observed by Parker Solar Probe
, ASTROPHYSICAL JOURNAL, Vol: 958, ISSN: 0004-637X -
Journal articleKuzichev IV, Vasko IY, Artemyev AV, et al., 2023,
Particle-in-Cell Simulations of Sunward and Anti-sunward Whistler Waves in the Solar Wind
, ASTROPHYSICAL JOURNAL, Vol: 959, ISSN: 0004-637X -
Journal articleKrasnoselskikh V, Zaslavsky A, Artemyev A, et al., 2023,
Ion Kinetics of Plasma Interchange Reconnection in the Lower Solar Corona
, ASTROPHYSICAL JOURNAL, Vol: 959, ISSN: 0004-637X -
Journal articleKlein KG, Spence H, Alexandrova O, et al., 2023,
HelioSwarm: a multipoint, multiscale mission to characterize turbulence
, Space Science Reviews, Vol: 219, ISSN: 0038-6308HelioSwarm (HS) is a NASA Medium-Class Explorer mission of the Heliophysics Division designed to explore the dynamic three-dimensional mechanisms controlling the physics of plasma turbulence, a ubiquitous process occurring in the heliosphere and in plasmas throughout the universe. This will be accomplished by making simultaneous measurements at nine spacecraft with separations spanning magnetohydrodynamic and sub-ion spatial scales in a variety of near-Earth plasmas. In this paper, we describe the scientific background for the HS investigation, the mission goals and objectives, the observatory reference trajectory and instrumentation implementation before the start of Phase B. Through multipoint, multiscale measurements, HS promises to reveal how energy is transferred across scales and boundaries in plasmas throughout the universe.
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Journal articleHartinger MD, Elsden T, Archer MO, et al., 2023,
Properties of Magnetohydrodynamic normal modes in the Earth's magnetosphere
, JGR: Space Physics, Vol: 128, ISSN: 2169-9402The Earth's magnetosphere supports a variety of Magnetohydrodynamic (MHD) normal modes with Ultra Low Frequencies (ULF) including standing Alfvén waves and cavity/waveguide modes. Their amplitudes and frequencies depend in part on the properties of the magnetosphere (size of cavity, wave speed distribution). In this work, we use ∼13 years of Time History of Events and Macroscale Interactions during Substorms satellite magnetic field observations, combined with linearized MHD numerical simulations, to examine the properties of MHD normal modes in the region L > 5 and for frequencies <80 mHz. We identify persistent normal mode structure in observed dawn sector power spectra with frequency-dependent wave power peaks like those obtained from simulation ensemble averages, where the simulations assume different radial Alfvén speed profiles and magnetopause locations. We further show with both observations and simulations how frequency-dependent wave power peaks at L > 5 depend on both the magnetopause location and the location of peaks in the radial Alfvén speed profile. Finally, we discuss how these results might be used to better model radiation belt electron dynamics related to ULF waves.
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Journal articleRosenfeld D, Kokhanovsky A, Goren T, et al., 2023,
Frontiers in satellite‐based estimates of cloud‐mediated aerosol forcing
, Reviews of Geophysics, Vol: 61, ISSN: 8755-1209Atmospheric aerosols affect the Earth's climate in many ways, including acting as the seeds on which cloud droplets form. Since a large fraction of these particles is anthropogenic, the clouds' microphysical and radiative characteristics are influenced by human activity on a global scale leading to important climatic effects. The respective change in the energy budget at the top of the atmosphere is defined as the effective radiative forcing due to aerosol-cloud interaction (ERFaci). It is estimated that the ERFaci offsets presently nearly 1/4 of the greenhouse-induced warming, but the uncertainty is within a factor of two. A common method to calculate the ERFaci is by the multiplication of the susceptibility of the cloud radiative effect to changes in aerosols by the anthropogenic change of the aerosol concentration. This has to be done by integrating it over all cloud regimes. Here we review the various methods of the ERFaci estimation. Global measurements require satellites' global coverage. The challenge of quantifying aerosol amounts in cloudy atmospheres are met with the rapid development of novel methodologies reviewed here. The aerosol characteristics can be retrieved from space based on their optical properties, including polarization. The concentrations of the aerosols that serve as cloud drop condensation nuclei can be also estimated from their impact on the satellite-retrieved cloud drop number concentrations. These observations are critical for reducing the uncertainty in the ERFaci calculated from global climate models (GCMs), but further development is required to allow GCMs to properly simulate and benefit these novel observables.
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Journal articleHwang K-J, Nakamura R, Eastwood JP, et al., 2023,
Cross-scale processes of magnetic reconnection
, Space Science Reviews, Vol: 219, ISSN: 0038-6308Various physical processes in association with magnetic reconnection occur over multiple scales from the microscopic to macroscopic scale lengths. This paper reviews multi-scale and cross-scale aspects of magnetic reconnection revealed in the near-Earth space beyond the general global-scale features and magnetospheric circulation organized by the Dungey Cycle. Significant and novel advancements recently reported, in particular, since the launch of the Magnetospheric Multi-scale mission (MMS), are highlighted being categorized into different locations with different magnetic topologies. These potentially paradigm-shifting findings include shock and foreshock transient driven reconnection, magnetosheath turbulent reconnection, flow shear driven reconnection, multiple X-line structures generated in the dayside/flankside/nightside magnetospheric current sheets, development and evolution of reconnection-driven structures such as flux transfer events, flux ropes, and dipolarization fronts, and their interactions with ambient plasmas. The paper emphasizes key aspects of kinetic processes leading to multi-scale structures and bringing large-scale impacts of magnetic reconnection as discovered in the geospace environment. These key features can be relevant and applicable to understanding other heliospheric and astrophysical systems.
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Journal articleAfanasiev A, Vainio R, Trotta D, et al., 2023,
Self-consistent modeling of the energetic storm particle event of November 10, 2012
, ASTRONOMY & ASTROPHYSICS, Vol: 679, ISSN: 0004-6361 -
Journal articleEglinton TI, Graven HD, Raymond PA, et al., 2023,
Making the case for an International Decade of Radiocarbon
, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol: 381, ISSN: 1364-503XRadiocarbon (14C) is a critical tool for understanding the global carbon cycle. During the Anthropocene, two new processes influenced 14C in atmospheric, land and ocean carbon reservoirs. First, 14C-free carbon derived from fossil fuel burning has diluted 14C, at rates that have accelerated with time. Second, 'bomb' 14C produced by atmospheric nuclear weapon tests in the mid-twentieth century provided a global isotope tracer that is used to constrain rates of air-sea gas exchange, carbon turnover, large-scale atmospheric and ocean transport, and other key C cycle processes. As we write, the 14C/12C ratio of atmospheric CO2 is dropping below pre-industrial levels, and the rate of decline in the future will depend on global fossil fuel use and net exchange of bomb 14C between the atmosphere, ocean and land. This milestone coincides with a rapid increase in 14C measurement capacity worldwide. Leveraging future 14C measurements to understand processes and test models requires coordinated international effort-a 'decade of radiocarbon' with multiple goals: (i) filling observational gaps using archives, (ii) building and sustaining observation networks to increase measurement density across carbon reservoirs, (iii) developing databases, synthesis and modelling tools and (iv) establishing metrics for identifying and verifying changes in carbon sources and sinks. This article is part of the Theo Murphy meeting issue 'Radiocarbon in the Anthropocene'.
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Journal articleEglinton TI, Graven HD, Raymond PA, et al., 2023,
A special issue preface: radiocarbon in the Anthropocene
, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol: 381, ISSN: 1364-503XThe Anthropocene is defined by marked acceleration in human-induced perturbations to the Earth system. Anthropogenic emissions of CO2 and other greenhouse gases to the atmosphere and attendant changes to the global carbon cycle are among the most profound and pervasive of these perturbations. Determining the magnitude, nature and pace of these carbon cycle changes is crucial for understanding the future climate that ecosystems and humanity will experience and need to respond to. This special issue illustrates the value of radiocarbon as a tool to shed important light on the nature, magnitude and pace of carbon cycle change. This article is part of the Theo Murphy meeting issue 'Radiocarbon in the Anthropocene'.
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Journal articleSishtla CP, Pomoell J, Vainio R, et al., 2023,
Modelling the interaction of Alfvenic fluctuations with coronal mass ejections in the low solar corona
, ASTRONOMY & ASTROPHYSICS, Vol: 679, ISSN: 0004-6361 -
Journal articleBizien N, de Wit TD, Froment C, et al., 2023,
Are Switchback Boundaries Observed by Parker Solar Probe Closed?
, ASTROPHYSICAL JOURNAL, Vol: 958, ISSN: 0004-637X -
Journal articlePalmerio E, Maharana A, Lynch BJ, et al., 2023,
Modeling a Coronal Mass Ejection from an Extended Filament Channel. II. Interplanetary Propagation to 1 au
, ASTROPHYSICAL JOURNAL, Vol: 958, ISSN: 0004-637X -
Journal articleDunn C, Bowen TA, Mallet A, et al., 2023,
Effect of Spherical Polarization on the Magnetic Spectrum of the Solar Wind
, ASTROPHYSICAL JOURNAL, Vol: 958, ISSN: 0004-637X -
Journal articleKruparova O, Krupar V, Szabo A, et al., 2023,
Quasi-thermal Noise Spectroscopy Analysis of Parker Solar Probe Data: Improved Electron Density Model for Solar Wind
, ASTROPHYSICAL JOURNAL, Vol: 957, ISSN: 0004-637X -
Journal articleStephenson P, Beth A, Deca J, et al., 2023,
The source of electrons at comet 67P
, Monthly Notices of the Royal Astronomical Society, Vol: 525, Pages: 5041-5065, ISSN: 0035-8711We examine the origin of electrons in a weakly outgassing comet, using Rosetta mission data and a 3D collisional model of electrons at a comet. We have calculated a new data set of electron-impact ionization (EII) frequency throughout the Rosetta escort phase, with measurements of the Rosetta Plasma Consortium’s Ion and Electron Sensor (RPC/IES). The EII frequency is evaluated in 15-min intervals and compared to other Rosetta data sets. EII is the dominant source of electrons at 67P away from perihelion and is highly variable (by up to three orders of magnitude). Around perihelion, EII is much less variable and less efficient than photoionization at Rosetta. Several drivers of the EII frequency are identified, including magnetic field strength and the outgassing rate. Energetic electrons are correlated to the Rosetta-upstream solar wind potential difference, confirming that the ionizing electrons are solar wind electrons accelerated by an ambipolar field. The collisional test particle model incorporates a spherically symmetric, pure water coma and all the relevant electron-neutral collision processes. Electric and magnetic fields are stationary model inputs, and are computed using a fully kinetic, collision-less Particle-in-Cell simulation. Collisional electrons are modelled at outgassing rates of Q = 1026 s−1 and Q = 1.5 × 1027 s−1. Secondary electrons are the dominant population within a weakly outgassing comet. These are produced by collisions of solar wind electrons with the neutral coma. The implications of large ion flow speed estimates at Rosetta, away from perihelion, are discussed in relation to multi-instrument studies and the new results of the EII frequency obtained in this study.
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Journal articleZomerdijk-Russell S, Masters A, Sun WJ, et al., 2023,
Does reconnection only occur at points of maximum shear on Mercury’s dayside magnetopause?
, JGR: Space Physics, Vol: 128, ISSN: 2169-9402MESSENGER observations of large numbers of flux transfer events (FTEs) during dayside crossings of Mercury's magnetopause have shown that the highly dynamic Hermean magnetosphere is strongly driven by frequent and intense magnetic reconnection. Since FTEs are products of reconnection, study of them can reveal information about whether reconnection sites favor points of maximum shear on the magnetopause. Here, we analyze 201 FTEs formed under relatively stable upstream solar wind conditions as observed by MESSENGER during inbound magnetopause crossings. By modeling paths of these FTEs along the magnetopause, we determine the conditions and locations of the reconnection sites at which these FTEs were likely formed. The majority of these FTE formation paths were found to intersect with high-magnetic shear regions, defined as shear angles above 135°. Seven FTEs were found where the maximum shear angle possible between the reconnecting magnetic field lines was less than 80° and three of these had shear angles less than 70°, supporting the idea that very low-shear reconnection could be occurring on Mercury's dayside magnetopause under this global-scale picture of magnetic reconnection. Additionally, for the FTEs formed under these low-shear reconnection conditions, tracing a dominant X-line connecting points of maximum shear along the magnetopause that passes through a region of very low-shear may be difficult to justify, implying reconnection could be occurring anywhere along Mercury's magnetopause and may not be confined to points of maximum shear.
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Journal articleMozer FS, Agapitov O, Bale SD, et al., 2023,
Density Enhancement Streams in The Solar Wind
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 957, ISSN: 2041-8205 -
Journal articleTrotta D, Horbury TS, Lario D, et al., 2023,
Irregular Proton Injection to High Energies at Interplanetary Shocks
, The Astrophysical Journal Letters, Vol: 957, Pages: L13-L13, ISSN: 2041-8205<jats:title>Abstract</jats:title> <jats:p>How thermal particles are accelerated to suprathermal energies is an unsolved issue, crucial for many astrophysical systems. We report novel observations of irregular, dispersive enhancements of the suprathermal particle population upstream of a high-Mach-number interplanetary shock. We interpret the observed behavior as irregular “injections” of suprathermal particles resulting from shock front irregularities. Our findings, directly compared to self-consistent simulation results, provide important insights for the study of remote astrophysical systems where shock structuring is often neglected.</jats:p>
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Journal articleGuilbert-Lepoutre A, Benseguane S, Martinien L, et al., 2023,
Pits on Jupiter-family comets and the age of cometary surfaces
, The Planetary Science Journal, Vol: 4, ISSN: 2632-3338Large and deep depressions, also known as pits, are observed at the surface of all Jupiter-family comets (JFCs) imaged by spacecraft missions. They offer the opportunity to glimpse the subsurface characteristics of comet nuclei and study the complex interplay between surface structures and cometary activity. This work investigates the evolution of pits at the surface of 81P/Wild 2, 9P/Tempel 1, and 103P/Hartley 2, in continuation of the work by Benseguane et al. on 67P/Churyumov–Gerasimenko. Pits are selected across the surface of each nucleus, and high-resolution shape models are used to compute the energy they receive. A thermal evolution model is applied to constrain how cometary activity sustained under current illumination conditions could modify them. Similar to what was found for 67P, we show that erosion resulting from water-driven activity is primarily controlled by seasonal patterns that are unique to each comet as a consequence of their shape and rotational properties. However, progressive erosion sustained after multiple perihelion passages is not able to carve any of the observed pits. Instead, cometary activity tends to erase sharp morphological features; they become wider and shallower over time. Our results reinforce the evolutionary sequence evidenced from independent measurables to transform "young" cometary surfaces, with sharp surface topography prone to outbursts, into "old" cometary surfaces. Finally, we suggest that the mechanism at the origin of the pits on JFCs should be able to carve these structures in a region of the solar system where water ice does not sublimate; the Centaur phase thus appears critical to understand JFC surface properties.
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