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Journal articleLee D, Min S-K, Park I-H, et al., 2022,
Enhanced Role of Convection in Future Hourly Rainfall Extremes Over South Korea
, GEOPHYSICAL RESEARCH LETTERS, Vol: 49, ISSN: 0094-8276 -
Journal articleWilson LB, Goodrich KA, Turner DL, et al., 2022,
The need for accurate measurements of thermal velocity distribution functions in the solar wind
, FRONTIERS IN ASTRONOMY AND SPACE SCIENCES, Vol: 9, ISSN: 2296-987X- Cite
- Citations: 1
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Journal articleWimmer-Schweingruber RF, Andre N, Barabash S, et al., 2022,
STELLA-Potential European contributions to a NASA-led interstellar probe
, FRONTIERS IN ASTRONOMY AND SPACE SCIENCES, Vol: 9, ISSN: 2296-987X -
Journal articleMaunder ML, Foullon C, Forsyth R, et al., 2022,
Multi-Spacecraft Observations of an Interplanetary Coronal Mass Ejection Interacting with Two Solar-Wind Regimes Observed by the Ulysses and Twin-STEREO Spacecraft
, Solar Physics, Vol: 297, ISSN: 0038-0938We present a combined study of a coronal mass ejection (CME), revealed in a unique orbital configuration that permits the analysis of remote-sensing observations on 27 June 2007 from the twin Solar Terrestrial Relations Observatory (STEREO)-A and -B spacecraft and of its subsequent in situ counterpart outside the ecliptic plane, the interplanetary coronal mass ejection (ICME) observed on 04 July 2007 by Ulysses at 1.5 AU and heliographic-Earth-ecliptic coordinates system (HEE) 33° latitude and 49° longitude. We apply a triangulation method to the STEREO Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) COR2 coronagraph images of the CME, and a self-similar expansion fitting method to STEREO/SECCHI Heliospheric Imager (HI)-B. At Ulysses we observe: a preceding forward shock, followed by a sheath region, a magnetic cloud, a rear forward shock, followed by a compression region due to a succeeding high-speed stream (HSS) interacting with the ICME. From a minimum variance analysis (MVA) and a length-scale analysis we infer that the magnetic cloud at Ulysses, with a duration of 24 h, has a west-north-east configuration, length scale of ≈0.2 AU, and mean expansion speed of 14.2 km s<sup>−1</sup>. The relatively small size of this ICME is likely to be a result of its interaction with the succeeding HSS. This ICME differs from the previously known over-expanding types observed by Ulysses, in that it straddles a region between the slow and fast solar wind that in itself drives the rear shock. We describe the agreements and limitations of these observations in comparison with 3D magneto-hydrodynamic (MHD) heliospheric simulations of the ICME in the context of a complex solar-wind environment.
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Journal articleShort B, Malaspina DMM, Halekas J, et al., 2022,
Observations of Quiescent Solar Wind Regions with Near-<i>f</i> <sub>ce</sub> Wave Activity
, ASTROPHYSICAL JOURNAL, Vol: 940, ISSN: 0004-637X- Cite
- Citations: 4
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Journal articleBeth A, Gunell H, Simon Wedlund C, et al., 2022,
First investigation of the diamagnetic cavity boundary layer with a 1D3V PIC simulation
, Astronomy and Astrophysics: a European journal, Vol: 667, Pages: 1-16, ISSN: 0004-6361Context. Amongst the different features and boundaries encountered around comets, one remains of particular interest to the plasma community: the diamagnetic cavity. Crossed for the first time at 1P/Halley during the Giotto flyby in 1986 and later met more than 700 times by the ESA Rosetta spacecraft around Comet 67P/Churyumov-Gerasimenko, this region, almost free of any magnetic field, surrounds nuclei of active comets. However, previous observations and modelling of this part of the coma have not yet provided a definitive answer as to the origin of such a cavity and on its border, the diamagnetic cavity boundary layer.Aims. We investigate which forces and equilibrium might be at play and balance the magnetic pressure at this boundary down to the spatial and temporal scales of the electrons in the 1D collisionless case. In addition, we scrutinise assumptions made in magneto-hydrodynamic and hybrid simulations of this environment and check for their validity.Methods. We simulated this region at the electron scale by means of 1D3V particle-in-cell simulations and SMILEI code.Results. Across this layer, depending on the magnetic field strength, the electric field is governed by different equilibria, with a thin double-layer forming ahead. In addition, we show that the electron distribution function departs from Maxwellian and/or gyrotropic distributions and that electrons do not behave adiabatically. We demonstrate the need to investigate this region at the electron scale in depth with fully kinetic simulations.
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Journal articleMasters A, Sergis N, Sulaiman A, et al., 2022,
Near-magnetic-field-aligned energetic electrons above Saturn’s dark polar regions
, Journal of Geophysical Research: Space Physics, Vol: 127, Pages: 1-14, ISSN: 2169-9380Saturn's main auroral emissions define two oval-shaped regions, one encircling each magnetic pole. The regions at higher latitudes are generally “dark” (i.e., devoid of auroras), and are magnetically connected to the distant planetary magnetosphere where there is a much-debated interaction with the solar wind. Electric currents flow into the atmosphere along the magnetic field within these polar regions. Establishing whether polar magnetic flux is “open” or “closed” is key for diagnosing how the solar wind interaction works. Because energetic electrons moving almost parallel or anti-parallel to the magnetic field shed light on the field topology, we survey Cassini energetic particle data for rare instances when the spacecraft was able to measure these parts of the distribution in the polar field environment close to the planet. Over the entire mission we find 16 intervals when measurements at ∼0urn:x-wiley:21699380:media:jgra57498:jgra57498-math-0001 and ∼180urn:x-wiley:21699380:media:jgra57498:jgra57498-math-0002 pitch angles were made simultaneously without sunlight contamination. Across all the events, above-background field-aligned fluxes were measured intermittently by the >15 keV electron channels, extending up to ∼300 keV when present. Uni-directional anti-planetward fluxes were observed during 10 of the events, and bi-directional fluxes were observed during 6 of the events. We suggest the uni-directional anti-planetward fluxes indicate the presence of field-aligned beams, and that the bi-directional fluxes indicate regions of locally closed magnetic field. These results either mean the solar wind interaction is predominantly via global magnetic reconnection but is more complex than initially proposed, or that the interaction is instead predominantly “viscous-like” at Saturn.
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Journal articlePollock CJ, Chen L-J, Schwartz SJ, et al., 2022,
Dynamics of Earth's bow shock under near-radial interplanetary magnetic field conditions
, PHYSICS OF PLASMAS, Vol: 29, ISSN: 1070-664X- Cite
- Citations: 1
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Journal articleGoren T, Feingold G, Gryspeerdt E, et al., 2022,
Projecting stratocumulus transitions on the albedo-cloud fraction relationship reveals linearity of albedo to droplet concentrations
, Geophysical Research Letters, Vol: 49, ISSN: 0094-8276Satellite images show solid marine stratocumulus cloud decks (Sc) that break up over the remote oceans. The Sc breakup is initiated by precipitation and is accompanied by a strong reduction in the cloud radiative effect. Aerosol has been shown to delay the Sc breakup by postponing the onset of precipitation, however its climatic effect is uncertain. Here we introduce a new approach that allows us to re-cast currently observed cloud cover and albedo to their counterfactual cleaner world, enabling the first estimate of the radiative effect due to delayed cloud breakup. Using simple radiative approximation, the radiative forcing with respect to pre-industrial times due to delayed Sc breakup is −0.39 W m−2. The radiative effect changes nearly linearly with aerosol due to the droplet concentration control on the cloud cover, suggesting a potentially accelerated warming if the current trend of reduction in aerosol emissions continues.
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Journal articleLi Y, Tang Y, Toumi R, et al., 2022,
Revisiting the definition of rapid intensification of tropical cyclones by clustering the initial intensity and inner-core size
, Journal of Geophysical Research: Atmospheres, Vol: 127, ISSN: 2169-8996Rapid intensification (RI) of tropical cyclones (TCs) provides a great challenge in operational forecasting and contributes significantly to the development of major TCs. RI is commonly defined as an increase in the maximum sustained surface wind speed of at least a certain threshold within 24 hr. The most widely used threshold is 30 kt (15.4 m/s), which was determined statistically. Here we propose a new definition for RI by objectively clustering TCs using the intensification rate, initial intensity, and radius of the maximum wind speed (RMW). A group of 770 samples is separated at a threshold of 45 kt (23.2 m/s). The threshold is 40 kt (20.6 m/s) for the western North Atlantic, where TC size measurements are more reliable. Monte Carlo experiments demonstrate that the proposed threshold is robust even considering the uncertainty in RMW of as high as 30 km. We show that, when a TC undergoes RI, its maximum wind speed is approximately 60 ± 15 kt (30.9 ± 7.7 m/s) and the RMW is 45 ± 20 km. The new threshold outperforms the conventional threshold of 30 kt/24 hr in describing the bimodal distribution of lifetime maximum intensity and explaining the annual count of Category 5 TCs. This new definition provides a more physically based threshold and describes a more reliable representation of extreme events. Although more comparisons are needed for operational application, it is likely to be desirable for case-based process studies and could provide a more valuable metric for TC intensification classification and research.
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Journal articleTrotta D, Vuorinen L, Hietala H, et al., 2022,
Single-spacecraft techniques for shock parameters estimation: a systematic approach
, Frontiers in Astronomy and Space Sciences, Vol: 9, Pages: 1-16, ISSN: 2296-987XSpacecraft missions provide the unique opportunity to study the properties of collisionless shocks utilising in situ measurements. In the past years, several diagnostics have been developed to address key shock parameters using time series of magnetic field (and plasma) data collected by a single spacecraft crossing a shock front. A critical aspect of such diagnostics is the averaging process involved in the evaluation of upstream/downstream quantities. In this work, we discuss several of these techniques, with a particular focus on the shock obliquity (defined as the angle between the upstream magnetic field and the shock normal vector) estimation. We introduce a systematic variation of the upstream/downstream averaging windows, yielding to an ensemble of shock parameters, which is a useful tool to address the robustness of their estimation. This approach is first tested with a synthetic shock dataset compliant with the Rankine-Hugoniot jump conditions for a shock, including the presence of noise and disturbances. We then employ self-consistent, hybrid kinetic shock simulations to apply the diagnostics to virtual spacecraft crossing the shock front at various stages of its evolution, highlighting the role of shock-induced fluctuations in the parameters’ estimation. This approach has the strong advantage of retaining some important properties of collisionless shock (such as, for example, the shock front microstructure) while being able to set a known, nominal set of shock parameters. Finally, two recent observations of interplanetary shocks from the Solar Orbiter spacecraft are presented, to demonstrate the use of this systematic approach to real events of shock crossings. The approach is also tested on an interplanetary shock measured by the four spacecraft of the Magnetospheric Multiscale (MMS) mission. All the Python software developed and used for the diagnostics (SerPyShock) is made available for the public, including an example of parameter estimation fo
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Journal articleRandich S, Gilmore G, Magrini L, et al., 2022,
The <i>Gaia</i>-ESO Public Spectroscopic Survey: Implementation, data products, open cluster survey, science, and legacy
, ASTRONOMY & ASTROPHYSICS, Vol: 666, ISSN: 0004-6361- Cite
- Citations: 121
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Journal articleGilmore G, Randich S, Worley CC, et al., 2022,
The <i>Gaia</i>-ESO Public Spectroscopic Survey: Motivation, implementation, GIRAFFE data processing, analysis, and final data products☆
, ASTRONOMY & ASTROPHYSICS, Vol: 666, ISSN: 0004-6361- Cite
- Citations: 100
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Journal articleSparks N, Toumi R, 2022,
The dependence of tropical cyclone pressure tendency on size
, Geophysical Research Letters, Vol: 49, ISSN: 0094-8276Current theories of tropical cyclone (TC) intensification give little direct indication of the role of the TC size in intensity changes, although there are observations showing a relationship. We develop a new model of TC central pressure tendency where the pressure change can be expressed as exponential with a time constant determined by the ratio of radius maximum wind (Rmax) and the column inflow or outflow speed. An analysis of observations confirms the relationship which becomes more important for a larger pressure tendency and suggests an upper bound on pressure tendency for a given Rmax. The dependence of the pressure tendency on size poses a challenging constraint on the accurate forecasting of TCs in numerical weather prediction and climate models.
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Journal articleBowen TA, Chandran BDG, Squire J, et al., 2022,
In situ signature of cyclotron resonant heating in the solar wind
, Physical Review Letters, Vol: 129, Pages: 1-8, ISSN: 0031-9007The dissipation of magnetized turbulence is an important paradigm for describing heating and energy transfer in astrophysical environments such as the solar corona and wind; however, the specific collisionless processes behind dissipation and heating remain relatively unconstrained by measurements. Remote sensing observations have suggested the presence of strong temperature anisotropy in the solar corona consistent with cyclotron resonant heating. In the solar wind, in situ magnetic field measurements reveal the presence of cyclotron waves, while measured ion velocity distribution functions have hinted at the active presence of cyclotron resonance. Here, we present Parker Solar Probe observations that connect the presence of ion-cyclotron waves directly to signatures of resonant damping in observed proton-velocity distributions using the framework of quasilinear theory. We show that the quasilinear evolution of the observed distribution functions should absorb the observed cyclotron wave population with a heating rate of 10−14 W/m3, indicating significant heating of the solar wind.
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Journal articleWatson-Parris D, Christensen MW, Laurenson A, et al., 2022,
Shipping regulations lead to large reduction in cloud perturbations.
, Proceedings of the National Academy of Sciences of USA, Vol: 119, Pages: 1-5, ISSN: 0027-8424Global shipping accounts for 13% of global emissions of SO2, which, once oxidized to sulfate aerosol, acts to cool the planet both directly by scattering sunlight and indirectly by increasing the albedo of clouds. This cooling due to sulfate aerosol offsets some of the warming effect of greenhouse gasses and is the largest uncertainty in determining the change in the Earth's radiative balance by human activity. Ship tracks-the visible manifestation of the indirect of effect of ship emissions on clouds as quasi-linear features-have long provided an opportunity to quantify these effects. However, they have been arduous to catalog and typically studied only in particular regions for short periods of time. Using a machine-learning algorithm to automate their detection we catalog more than 1 million ship tracks to provide a global climatology. We use this to investigate the effect of stringent fuel regulations introduced by the International Maritime Organization in 2020 on their global prevalence since then, while accounting for the disruption in global commerce caused by COVID-19. We find a marked, but clearly nonlinear, decline in ship tracks globally: An 80% reduction in SO[Formula: see text] emissions causes only a 25% reduction in the number of tracks detected.
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Journal articleKourgialas NN, Hliaoutakis A, Argyriou A, et al., 2022,
A web-based GIS platform supporting innovative irrigation management techniques at farm-scale for the Mediterranean island of Crete
, SCIENCE OF THE TOTAL ENVIRONMENT, Vol: 842, ISSN: 0048-9697 -
Journal articleLaker R, Horbury TS, Matteini L, et al., 2022,
Switchback deflections beyond the early parker solar probe encounters
, Monthly Notices of the Royal Astronomical Society, Vol: 517, Pages: 1001-1005, ISSN: 0035-8711Switchbacks are Aflvénic fluctuations in the solar wind, which exhibit large rotations in the magnetic field direction. Observations from Parker Solar Probe’s (PSP’s) first two solar encounters have formed the basis for many of the described switchback properties and generation mechanisms. However, this early data may not be representative of the typical near-Sun solar wind, biasing our current understanding of these phenomena. One defining switchback property is the magnetic deflection direction. During the first solar encounter, this was primarily in the tangential direction for the longest switchbacks, which has since been discussed as evidence, and a testable prediction, of several switchback generation methods. In this study, we re-examine the deflection direction of switchbacks during the first eight PSP encounters to confirm the existence of a systematic deflection direction. We first identify switchbacks exceeding a threshold deflection in the magnetic field and confirm a previous finding that they are arc-polarized. In agreement with earlier results from PSP’s first encounter, we find that groups of longer switchbacks tend to deflect in the same direction for several hours. However, in contrast to earlier studies, we find that there is no unique direction for these deflections, although several solar encounters showed a non-uniform distribution in deflection direction with a slight preference for the tangential direction. This result suggests a systematic magnetic configuration for switchback generation, which is consistent with interchange reconnection as a source mechanism, although this new evidence does not rule out other mechanisms, such as the expansion of wave modes.
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Journal articleSparks N, Toumi R, 2022,
A physical model of tropical cyclone central pressure filling at landfall
, Journal of the Atmospheric Sciences, Vol: 79, Pages: 2585-2599, ISSN: 0022-4928We derive a simple physically based analytic model which describes the pressure filling of a tropical cyclone (TC) over land. Starting from the axisymmetric mass continuity equation in cylindrical coordinates we derive that the half-life decay of the pressure deficit between the environmentand TC centre is proportional to the initial radius of maximum surface wind speed. The initial pressure deficit and column-mean radial inflow speed into the core are the other key variables. The assumptions made in deriving the model are validated against idealised numerical simulations of TC decay over land. Decay half-lives predicted from a range of initial TC states are tested against the idealized simulations and are in good agreement. Dry idealised TC decay simulations show that without latent convective heating, the boundary layer decouples from the vortex above leading to a fast decay of surface winds while a mid-level vortex persists.
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Journal articleTelloni D, Adhikari L, Zank GP, et al., 2022,
Observation and Modeling of the Solar Wind Turbulence Evolution in the Sub-Mercury Inner Heliosphere
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 938, ISSN: 2041-8205- Cite
- Citations: 13
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Journal articleBadman ST, Carley E, Canizares LA, et al., 2022,
Tracking a Beam of Electrons from the Low Solar Corona into Interplanetary Space with the Low Frequency Array, Parker Solar Probe, and 1 au Spacecraft
, ASTROPHYSICAL JOURNAL, Vol: 938, ISSN: 0004-637X- Cite
- Citations: 16
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Journal articleZhao J, Malaspina DM, de Wit TD, et al., 2022,
Broadband Electrostatic Waves near the Lower-hybrid Frequency in the Near-Sun Solar Wind Observed by the Parker Solar Probe
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 938, ISSN: 2041-8205- Cite
- Citations: 3
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Journal articleOwen CJ, Abraham JB, Nicolaou G, et al., 2022,
Solar Orbiter SWA Observations of Electron Strahl Properties Inside 1 AU
, UNIVERSE, Vol: 8- Cite
- Citations: 3
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Journal articleSchwartz SJ, Goodrich KA, Wilson LB, et al., 2022,
Energy Partition at Collisionless Supercritical Quasi-Perpendicular Shocks
, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 127, ISSN: 2169-9380- Cite
- Citations: 5
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Journal articleBrandt PC, Provornikova EA, Cocoros A, et al., 2022,
Interstellar Probe: Humanity?s exploration of the Galaxy Begins
, ACTA ASTRONAUTICA, Vol: 199, Pages: 364-373, ISSN: 0094-5765- Cite
- Citations: 21
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Journal articleWells CD, Kasoar M, Bellouin N, et al., 2022,
Supplementary material to "Local and remote climate impacts of future African aerosol emissions"
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Journal articleAgiwal O, Moore L, Martinis C, et al., 2022,
First Steps Towards a New Saturn Ionosphere Model Including Ring-Planet Coupling and Electrodynamics
<jats:p>&lt;div&gt;&lt;div&gt;&lt;div&gt;&lt;div&gt;The Cassini Grand Finale revealed that there is still much that we do not understand about Saturn&amp;#8217;s upper atmosphere. In-situ observations reveal highly complex coupling between the planetary atmosphere and rings and inter-hemispheric electrodynamic coupling at latitudes that are magnetically connected to the intra D-ring region in the magnetosphere. Current Saturn models are ill-suited to treating electrodynamics and ring-planet interactions at Saturn. Thus, we adapt SAMI, a well-known terrestrial ionosphere model that is flux-tube based and already includes electrodynamics, to Saturn, with the aim of using it in conjunction with existing Saturn models such as the STIM-GCM (Saturn Thermosphere Ionosphere Model) to decipher the long-standing unexplained morphologies in Saturn&amp;#8217;s ionosphere and investigate the ring-atmosphere coupling and electrodynamics revealed by the Cassini end-of-mission data. We will present initial results having adapted SAMI to Saturn, showing the full extent of the atmospheric chemistry and model capabilities at present. We will discuss future directions of development towards the construction of the new model capable of resolving the complex ring-atmosphere coupling and electrodynamics, and the possibility of adapting this model to other planets.&lt;/div&gt;&lt;/div&gt;&lt;/div&gt;&lt;/div&gt;</jats:p>
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Journal articleGrant S, Jones G, Owen C, et al., 2022,
The Prediction of, and Results from Solar Orbiter's encounter with Comet C/2021 A1 (Leonard).
<jats:p>&lt;p&gt;As the solar wind encounters a comet, ionized gas released from the nucleus propagates away from the Sun with the wind, forming the ion tail of the comet that can stretch for multiple astronomical units. The transport of cometary material antisunward of the comet provides opportunities to measure the cometary composition and plasma interactions at a significant distance from a comet&amp;#8217;s nucleus. Serendipitous crossings by spacecraft of comets&amp;#8217; ion tails is a surprisingly commonplace occurrence, but can go unnoticed, as any measured plasma fluctuations can be small.&lt;/p&gt;&lt;p&gt;Using the measured flow of the solar wind at the spacecraft, we can estimate the motion of the solar plasma upstream of the spacecraft, and compare this trajectory with the locations of known comets. This method can uncover previously unnoticed ion tail encounters and predict future encounters.&lt;/p&gt;&lt;p&gt;In December 2021, while comet C/2021 A1 (Leonard) traversed the ecliptic plane, sunward of the spacecraft Solar Orbiter, the spacecraft was immersed in the comet&amp;#8217;s ion tail. This encounter was predicted using a range of estimated solar wind velocities to estimate the motion of solar wind plasma to the spacecraft. A wealth of data was collected during the encounter, including results from multiple instruments that support the prediction. We present data returned from the SWA and magnetometer instruments, providing information on the structure of the induced magnetotail. Additionally, images of comet Leonard&amp;#8217;s ion tail from other spacecraft during the encounter provide a uniquely complete picture of the tail crossing.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;em&gt;Fig: Orbital configuration of comet Leonard and Sola
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Journal articleKaweeyanun N, Masters A, 2022,
Can Ganymede's magnetopause help us probe its subsurface ocean?
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Conference paperStephenson P, Galand M, Deca J, et al., 2022,
Cold electrons at a weakly outgassing comet
, Europlanet Science Congress 2022, Publisher: Copernicus GmbH
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