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  • Journal article
    Archer M, Hartinger MD, Rastatter L, Southwood D, Heyns M, Eggington J, Wright A, Plaschke F, Shi Xet al., 2023,

    Auroral, ionospheric and ground magnetic signatures of magnetopause surface modes

    , Journal of Geophysical Research: Space Physics, Vol: 128, Pages: 1-25, ISSN: 2169-9380

    Surface waves on Earth's magnetopause have a controlling effect upon global magnetospheric dynamics. Since spacecraft provide sparse in situ observation points, remote sensing these modes using ground-based instruments in the polar regions is desirable. However, many open conceptual questions on the expected signatures remain. Therefore, we provide predictions of key qualitative features expected in auroral, ionospheric, and ground magnetic observations through both magnetohydrodynamic theory and a global coupled magnetosphere-ionosphere simulation of a magnetopause surface eigenmode. These show monochromatic oscillatory field-aligned currents (FACs), due to both the surface mode and its non-resonant Alfvén coupling, are present throughout the magnetosphere. The currents peak in amplitude at the equatorward edge of the magnetopause boundary layer, not the open-closed boundary as previously thought. They also exhibit slow poleward phase motion rather than being purely evanescent. We suggest the upward FAC perturbations may result in periodic auroral brightenings. In the ionosphere, convection vortices circulate the poleward moving FAC structures. Finally, surface mode signals are predicted in the ground magnetic field, with ionospheric Hall currents rotating perturbations by approximately (but not exactly) 90° compared to the magnetosphere. Thus typical dayside magnetopause surface modes should be strongest in the East-West ground magnetic field component. Overall, all ground-based signatures of the magnetopause surface mode are predicted to have the same frequency across L-shells, amplitudes that maximize near the magnetopause's equatorward edge, and larger latitudinal scales than for field line resonance. Implications in terms of ionospheric Joule heating and geomagnetically induced currents are discussed.

  • Journal article
    Brandt PC, Provornikova E, Bale SD, Cocoros A, DeMajistre R, Dialynas K, Elliott HA, Eriksson S, Fields B, Galli A, Hill ME, Horanyi M, Horbury T, Hunziker S, Kollmann P, Kinnison J, Fountain G, Krimigis SM, Kurth WS, Linsky J, Lisse CM, Mandt KE, Magnes W, McNutt RL, Miller J, Moebius E, Mostafavi P, Opher M, Paxton L, Plaschke F, Poppe AR, Roelof EC, Runyon K, Redfield S, Schwadron N, Sterken V, Swaczyna P, Szalay J, Turner D, Vannier H, Wimmer-Schweingruber R, Wurz P, Zirnstein EJet al., 2023,

    Future Exploration of the Outer Heliosphere and Very Local Interstellar Medium by Interstellar Probe

    , SPACE SCIENCE REVIEWS, Vol: 219, ISSN: 0038-6308
  • Journal article
    Gieseler J, Dresing N, Palmroos C, von Forstner JLFL, Price DJ, Vainio R, Kouloumvakos A, Rodriguez-Garcia L, Trotta D, Genot V, Masson A, Roth M, Veronig Aet al., 2023,

    Solar-MACH: An open-source tool to analyze solar magnetic connection configurations

    , FRONTIERS IN ASTRONOMY AND SPACE SCIENCES, Vol: 9, ISSN: 2296-987X
  • Journal article
    Sibeck DGG, Murphy KRR, Porter FS, Connor HKK, Walsh BMM, Kuntz KDD, Zesta E, Valek P, Baker CLL, Goldstein J, Frey H, Hsieh S-Y, Brandt PCC, Gomez R, DiBraccio GAA, Kameda S, Dwivedi V, Purucker MEE, Shoemaker M, Petrinec SMM, Aryan H, Desai RTT, Henderson MGG, Cucho-Padin G, Cramer WDet al., 2023,

    Quantifying the global solar wind-magnetosphere interaction with the Solar-Terrestrial Observer for the Response of the Magnetosphere (STORM) mission concept

    , FRONTIERS IN ASTRONOMY AND SPACE SCIENCES, Vol: 10, ISSN: 2296-987X
  • Journal article
    Krasnoselskikh V, Tsurutani BT, Dudok de Wit T, Walker S, Balikhin M, Balat-Pichelin M, Velli M, Bale SD, Maksimovic M, Agapitov O, Baumjohann W, Berthomier M, Bruno R, Cranmer SR, de Pontieu B, Meneses DDS, Eastwood J, Erdelyi R, Ergun R, Fedun V, Ganushkina N, Greco A, Harra L, Henri P, Horbury T, Hudson H, Kasper J, Khotyaintsev Y, Kretzschmar M, Krucker S, Kucharek H, Langevin Y, Lavraud B, Lebreton J-P, Lepri S, Liemohn M, Louarn P, Moebius E, Mozer F, Nemecek Z, Panasenco O, Retino A, Safrankova J, Scudder J, Servidio S, Sorriso-Valvo L, Souček J, Szabo A, Vaivads A, Vekstein G, Vörös Z, Zaqarashvili T, Zimbardo G, Fedorov Aet al., 2023,

    ICARUS: in-situ studies of the solar corona beyond Parker Solar Probe and Solar Orbiter

    , Experimental Astronomy, Vol: 54, Pages: 277-315, ISSN: 0922-6435

    The primary scientific goal of ICARUS (Investigation of Coronal AcceleRation and heating of solar wind Up to the Sun), a mother-daughter satellite mission, proposed in response to the ESA “Voyage 2050” Call, will be to determine how the magnetic field and plasma dynamics in the outer solar atmosphere give rise to the corona, the solar wind, and the entire heliosphere. Reaching this goal will be a Rosetta Stone step, with results that are broadly applicable within the fields of space plasma physics and astrophysics. Within ESA’s Cosmic Vision roadmap, these science goals address Theme 2: “How does the Solar System work?” by investigating basic processes occurring “From the Sun to the edge of the Solar System”. ICARUS will not only advance our understanding of the plasma environment around our Sun, but also of the numerous magnetically active stars with hot plasma coronae. ICARUS I will perform the first direct in situ measurements of electromagnetic fields, particle acceleration, wave activity, energy distribution, and flows directly in the regions in which the solar wind emerges from the coronal plasma. ICARUS I will have a perihelion altitude of 1 solar radius and will cross the region where the major energy deposition occurs. The polar orbit of ICARUS I will enable crossing the regions where both the fast and slow winds are generated. It will probe the local characteristics of the plasma and provide unique information about the physical processes involved in the creation of the solar wind. ICARUS II will observe this region using remote-sensing instruments, providing simultaneous, contextual information about regions crossed by ICARUS I and the solar atmosphere below as observed by solar telescopes. It will thus provide bridges for understanding the magnetic links between the heliosphere and the solar atmosphere. Such information is crucial to our understanding of the plasma physics and electrodynamics of the solar atmosph

  • Journal article
    Shi C, Velli M, Lionello R, Sioulas N, Huang Z, Halekas JS, Tenerani A, Reville V, Dakeyo J-B, Maksimovic M, Bale SDet al., 2023,

    Proton and Electron Temperatures in the Solar Wind and Their Correlations with the Solar Wind Speed

    , ASTROPHYSICAL JOURNAL, Vol: 944, ISSN: 0004-637X
  • Journal article
    McComas DJ, Sharma T, Christian ER, Cohen CMS, Desai MI, Hill ME, Khoo LY, Matthaeus WH, Mitchell DG, Pecora F, Rankin JS, Schwadron NA, Szalay JR, Shen MM, Braga CR, Mostafavi PS, Bale SDet al., 2023,

    Parker Solar Probe Encounters the Leg of a Coronal Mass Ejection at 14 Solar Radii

    , ASTROPHYSICAL JOURNAL, Vol: 943, ISSN: 0004-637X
  • Journal article
    Raouafi NE, Matteini L, Squire J, Badman ST, Velli M, Klein KG, Chen CHK, Matthaeus WH, Szabo A, Linton M, Allen RC, Szalay JR, Bruno R, Decker RB, Akhavan-Tafti M, Agapitov OV, Bale SD, Bandyopadhyay R, Battams K, Berčič L, Bourouaine S, Bowen T, Cattell C, Chandran BDG, Chhiber R, Cohen CMS, D'Amicis R, Giacalone J, Hess P, Howard RA, Horbury TS, Jagarlamudi VK, Joyce CJ, Kasper JC, Kinnison J, Laker R, Liewer P, Malaspina DM, Mann I, McComas DJ, Niembro-Hernandez T, Panasenco O, Pokorný P, Pusack A, Pulupa M, Perez JC, Riley P, Rouillard AP, Shi C, Stenborg G, Tenerani A, Verniero JL, Viall N, Vourlidas A, Wood BE, Woodham LD, Woolley Tet al., 2023,

    Parker solar probe: four years of discoveries at solar cycle minimum

    , Space Science Reviews, Vol: 219, Pages: 1-140, ISSN: 0038-6308

    Launched on 12 Aug. 2018, NASA’s Parker Solar Probe had completed 13 of its scheduled 24 orbits around the Sun by Nov. 2022. The mission’s primary science goal is to determine the structure and dynamics of the Sun’s coronal magnetic field, understand how the solar corona and wind are heated and accelerated, and determine what processes accelerate energetic particles. Parker Solar Probe returned a treasure trove of science data that far exceeded quality, significance, and quantity expectations, leading to a significant number of discoveries reported in nearly 700 peer-reviewed publications. The first four years of the 7-year primary mission duration have been mostly during solar minimum conditions with few major solar events. Starting with orbit 8 (i.e., 28 Apr. 2021), Parker flew through the magnetically dominated corona, i.e., sub-Alfvénic solar wind, which is one of the mission’s primary objectives. In this paper, we present an overview of the scientific advances made mainly during the first four years of the Parker Solar Probe mission, which go well beyond the three science objectives that are: (1) Trace the flow of energy that heats and accelerates the solar corona and solar wind; (2) Determine the structure and dynamics of the plasma and magnetic fields at the sources of the solar wind; and (3) Explore mechanisms that accelerate and transport energetic particles.

  • Journal article
    Liu YD, Ran H, Hu H, Bale SDet al., 2023,

    On the Generation and Evolution of Switchbacks and the Morphology of the Alfvenic Transition: Low Mach-number Boundary Layers

    , ASTROPHYSICAL JOURNAL, Vol: 944, ISSN: 0004-637X
  • Journal article
    Trattner KJ, Fuselier SA, Schwartz SJ, Kucharek H, Burch JL, Ergun RE, Petrinec SM, Madanian Het al., 2023,

    Ion Acceleration at the Quasi-Parallel Shock: The Source Distributions of the Diffuse Ions

    , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 128, ISSN: 2169-9380
  • Journal article
    Moses JI, Brown ZL, Koskinen TT, Fletcher LN, Serigano J, Guerlet S, Moore L, Waite JH, Ben-Jaffel L, Galand M, Chadney JM, Hörst SM, Sinclair JA, Vuitton V, Müller-Wodarg Iet al., 2023,

    Saturn’s atmospheric response to the large influx of ring material inferred from Cassini INMS measurements

    , Icarus, Vol: 391, Pages: 1-40, ISSN: 0019-1035

    During the Grand Finale stage of the Cassini mission, organic-rich ring material was discovered to be flowing into Saturn’s equatorial upper atmosphere at a surprisingly large rate. Through a series of photochemical models, we have examined the consequences of this ring material on the chemistry of Saturn’s neutral and ionized atmosphere. We find that if a substantial fraction of this material enters the atmosphere as vapor or becomes vaporized as the solid ring particles ablate upon atmospheric entry, then the ring-derived vapor would strongly affect the composition of Saturn’s ionosphere and neutral stratosphere. Our surveys of Cassini infrared and ultraviolet remote-sensing data from the final few years of the mission, however, reveal none of these predicted chemical consequences. We therefore conclude that either (1) the inferred ring influx represents an anomalous, transient situation that was triggered by some recent dynamical event in the ring system that occurred a few months to a few tens of years before the 2017 end of the Cassini mission, or (2) a large fraction of the incoming material must have been entering the atmosphere as small dust particles less than 100 nm in radius, rather than as vapor or as large particles that are likely to ablate. Future observations or upper limits for stratospheric neutral species such as HCN, HCN, and CO at infrared wavelengths could shed light on the origin, timing, magnitude, and nature of a possible vapor-rich ring-inflow event.

  • Journal article
    Phillips C, Bandyopadhyay R, McComas DJ, Bale SDet al., 2023,

    Association of intermittency with electron heating in the near-Sun solar wind

    , MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 519, Pages: L1-L4, ISSN: 0035-8711
  • Journal article
    Trotta D, Hietala H, Horbury T, Dresing N, Vainio R, Wilson L, Plotnikov I, Kilpua Eet al., 2023,

    Multi-spacecraft observations of shocklets at an interplanetary shock

    , MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 520, Pages: 437-445, ISSN: 0035-8711
  • Journal article
    Zomerdijk-Russell S, Masters A, Korth H, Heyner Det al., 2023,

    Modelling the time-dependent magnetic fields that BepiColombo will use to probe down into Mercury’s mantle

    , Geophysical Research Letters, Vol: 50, ISSN: 0094-8276

    External solar wind variability causes motion of the magnetopause and changes of this boundary's current structure, and the resulting inductive processes, may be exploited to determine the interior structure of magnetized planets. In preparation for the arrival of the BepiColombo spacecraft at Mercury, we here assess solar wind ram pressure forcing in this planet's environment, through analysis of data acquired by the Helios spacecraft, and the impact on the magnetopause's inducing field. These measurements suggest that BepiColombo will see highly unpredictable solar wind conditions and that the inducing field generated in response to variable solar wind ram pressure is non-uniform across the planet's surface. The inducing magnetic field spectrum, with frequencies in the range of ∼5.5 x10¯⁵ -1.5 x 10¯²Hz, suggests that the transfer functions derived from the two BepiColombo spacecraft could allow us to obtain a profile of conductivity through Mercury's crust and mantle.

  • Journal article
    De Marco R, Bruno R, Jagarlamudi VK, D'Amicis R, Marcucci MF, Fortunato V, Perrone D, Telloni D, Owen CJ, Louarn P, Fedorov A, Livi S, Horbury Tet al., 2023,

    Innovative technique for separating proton core, proton beam, and alpha particles in solar wind 3D velocity distribution functions

    , ASTRONOMY & ASTROPHYSICS, Vol: 669, ISSN: 0004-6361
  • Journal article
    Maffei S, Eggington JWB, Livermore PW, Mound JE, Sanchez S, Eastwood JP, Freeman MPet al., 2023,

    Climatological predictions of the auroral zone locations driven by moderate and severe space weather events

    , Scientific Reports, Vol: 13, Pages: 1-11, ISSN: 2045-2322

    Auroral zones are regions where, in an average sense, aurorae due to solar activity are most likely spotted. Their shape and, similarly, the geographical locations most vulnerable to extreme space weather events (which we term ‘danger zones’) are modulated by Earth’s time-dependent internal magnetic field whose structure changes on yearly to decadal timescales. Strategies for mitigating ground-based space weather impacts over the next few decades can benefit from accurate forecasts of this evolution. Existing auroral zone forecasts use simplified assumptions of geomagnetic field variations. By harnessing the capability of modern geomagnetic field forecasts based on the dynamics of Earth’s core we estimate the evolution of the auroral zones and of the danger zones over the next 50 years. Our results predict that space-weather related risk will not change significantly in Europe, Australia and New Zealand. Mid-to-high latitude cities such as Edinburgh, Copenhagen and Dunedin will remain in high-risk regions. However, northward change of the auroral and danger zones over North America will likely cause urban centres such as Edmonton and Labrador City to be exposed by 2070 to the potential impact of severe solar activity.

  • Journal article
    Clear CP, Uylings P, Raassen T, Nave G, Pickering JCet al., 2023,

    New Ritz wavelengths and transition probabilities for parity-forbidden, singly ionized nickel [Ni II] lines of astrophysical interest

    , Monthly Notices of the Royal Astronomical Society, Vol: 519, Pages: 4040-4046, ISSN: 0035-8711

    We report accurate Ritz wavelengths for parity-forbidden [Ni II] transitions, derived from energy levels determined using high-resolution Fourier transform spectroscopy. Transitions between the 18 lowest Ni II energy levels of even-parity produced Ritz wavelengths for 126 parity-forbidden lines. Uncertainties for the Ritz wavelengths derived in this work are up to two orders of magnitude lower than previously published values. Transition probabilities were calculated using the semi-empirical orthogonal operator method, with uncertainties ranging from approximately 1 per cent for strong M1 lines and up to 10 per cent for weak E2 lines. Accurate forbidden line wavelengths and transition probabilities, particularly for lines in the infrared, are important in the analyses of low-density astrophysical plasmas, such as supernova remnants, planetary nebulae, and active galactic nuclei.

  • Journal article
    Breul P, Ceppi P, Shepherd TG, 2023,

    Revisiting the wintertime emergent constraint of the southern hemispheric midlatitude jet response to global warming

    , Weather and Climate Dynamics, Vol: 4, Pages: 39-47, ISSN: 2698-4016

    Most climate models show a poleward shift of the southern hemispheric zonal-mean jet in response to climate change, but the inter-model spread is large. In an attempt to constrain future jet responses, past studies have identified an emergent constraint between the climatological jet latitude and the future jet shift in austral winter. However, we show that the emergent constraint only arises in the zonal mean and not in separate halves of the hemisphere, which questions the physicality of the emergent constraint. We further find that the zonal-mean jet latitude does not represent the latitude of a zonally coherent structure, due to the presence of a double-jet structure in the Pacific region during this season. The zonal asymmetry causes the previously noted large spread in the zonal-mean climatology but not in the response, which underlies the emergent constraint. We therefore argue that the emergent constraint on the zonal-mean jet cannot narrow down the spread in future wind responses, and we propose that emergent constraints on the jet response in austral winter should be based on regional rather than zonal-mean circulation features.

  • Journal article
    Vuorinen L, Lamoury A, Masongsong E, Hietala Het al., 2023,

    SPACE RAINDROPS SPLASHING ON EARTH’S MAGNETIC UMBRELLA

    , Eos (United States), Vol: 104, Pages: 35-39, ISSN: 0096-3941

    Every few minutes, enormous “droplets” of plasma rain down from space toward Earth. Instead of crashing catastrophically to the ground, these droplets, called magnetosheath jets, are deflected by the outer reaches of Earth’s magnetic field. Despite the frequent occurrence of magnetosheath jets near Earth and their likely ubiquity across the solar system, their study is young and there is much we do not know about their origins and behavior. Specifi-cally, their potential effects on space weather—the phenomena we experience on Earth due to the ever changing stream of plasma that flows through our solar system—are unclear and still being investigated. Therefore, these jets are currently not factored into space weather models or predictions. Here we dis-cuss recent findings in this field and important questions that remain to be answered.

  • Journal article
    Lotz S, Nel AE, Wicks RT, Roberts OW, Engelbrecht NE, Strauss RD, Botha GJJ, Kontar EP, Pitna A, Bale SDet al., 2023,

    The Radial Variation of the Solar Wind Turbulence Spectra near the Kinetic Break Scale from Parker Solar Probe Measurements

    , ASTROPHYSICAL JOURNAL, Vol: 942, ISSN: 0004-637X
  • Conference paper
    Eckersley S, Rowe S, Hill W, Forsyth C, Wicks R, Eastwood J, Brown P, Dániel V, Gromeš J, Junas M, Ryden K, Heil M, Terzo S, Gonzalo AR, Jiggens Pet al., 2023,

    An ESA Nanosatellite Constellation to Monitor Space Weather Effects

    , ISSN: 0074-1795

    Major space weather events have the potential to cause significant damage and disruption to critical terrestrial and space-based infrastructure, including radio communication networks, Global Navigation Satellite Systems (GNSS) and the electricity grid. The continuous monitoring of space weather is therefore crucial for providing advanced warning of potentially destructive events. The European Space Agency (ESA) is in the process of developing the Enhanced Space Weather Monitoring System, which will utilise spacecraft to monitor space weather on and away from the Sun-Earth line (e.g., the ESA Vigil mission). The Distributed Space Weather Sensor System (D3S) will form part of this Enhanced Space Weather Monitoring System and focus on making measurements in the vicinity of the Earth. In early 2021, SSTL was selected to lead an ESA-funded Phase 0/A study titled “SSA P3-SWE-LIII Nanosatellites for D3S”. The aim of the study was to establish the role that nanosatellites can play as part of the D3S space weather monitoring system. Nanosatellite technologies have seen significant performance and capability improvements in recent years, and this was one of the reasons that nanosatellites were of particular interest for this study, along with the benefit of their small size and lower costs. The objective of the Phase 0 study was to analyse the space weather measurement requirements for the mission and identify potential space weather instruments that could be accommodated on a nanosatellite mission. A trade-off of a range of different mission architecture concepts was conducted, and the two most promising concepts were selected for more detailed analysis in the latter half of the Phase 0 study. At the end of Phase 0, ESA selected a concept comprising 6x 16U SSTL CubeSats in a 500-600km Sun-Synchronous Orbit to take forward into Phase A for further definition. The Phase A study focussed on the more detailed design of a precursor demonstration mission comprised of

  • Journal article
    Sioulas N, Huang Z, Shi C, Velli M, Tenerani A, Bowen TA, Bale SD, Huang J, Vlahos L, Woodham LD, Horbury TS, de Wit TD, Larson D, Kasper J, Owen CJ, Stevens ML, Case A, Pulupa M, Malaspina DM, Bonnell JW, Livi R, Goetz K, Harvey PR, MacDowall RJ, Maksimovic M, Louarn P, Fedorov Aet al., 2023,

    Magnetic field spectral evolution in the inner heliosphere

    , Letters of the Astrophysical Journal, Vol: 943, Pages: 1-7, ISSN: 2041-8205

    Parker Solar Probe and Solar Orbiter data are used to investigate the radial evolution of magnetic turbulence between 0.06 ≲ R ≲ 1 au. The spectrum is studied as a function of scale, normalized to the ion inertial scale di. In the vicinity of the Sun, the inertial range is limited to a narrow range of scales and exhibits a power-law exponent of, αB = −3/2, independent of plasma parameters. The inertial range grows with distance, progressively extending to larger spatial scales, while steepening toward a αB = −5/3 scaling. It is observed that spectra for intervals with large magnetic energy excesses and low Alfvénic content steepen significantly with distance, in contrast to highly Alfvénic intervals that retain their near-Sun scaling. The occurrence of steeper spectra in slower wind streams may be attributed to the observed positive correlation between solar wind speed and Alfvénicity.

  • Journal article
    Gingell I, Schwartz SJ, Kucharek H, Farrugia CJ, Fryer LJ, Plank J, Trattner KJet al., 2023,

    Hybrid simulations of the decay of reconnected structures downstream of the bow shock

    , PHYSICS OF PLASMAS, Vol: 30, ISSN: 1070-664X
  • Journal article
    Sun J, Vasko IY, Bale SD, Wang R, Mozer FSet al., 2022,

    Double Layers in the Earth's Bow Shock

    , GEOPHYSICAL RESEARCH LETTERS, Vol: 49, ISSN: 0094-8276
  • Journal article
    Xie X, Myhre G, Shindell D, Faluvegi G, Takemura T, Voulgarakis A, Shi Z, Li X, Xie X, Liu H, Liu X, Liu Yet al., 2022,

    Anthropogenic sulfate aerosol pollution in South and East Asia induces increased summer precipitation over arid Central Asia

    , COMMUNICATIONS EARTH & ENVIRONMENT, Vol: 3
  • Journal article
    Perrone D, Perri S, Bruno R, Stansby D, D'Amicis R, Jagarlamudi VK, Laker R, Toledo-Redondo S, Stawarz JE, Telloni D, De Marco R, Owen CJ, Raines JM, Settino A, Lavraud B, Maksimovic M, Vaivads A, Phan TD, Fargette N, Louarn P, Zouganelis Iet al., 2022,

    Evolution of coronal hole solar wind in the inner heliosphere: Combined observations by Solar Orbiter and Parker Solar Probe

    , ASTRONOMY & ASTROPHYSICS, Vol: 668, ISSN: 0004-6361
  • Journal article
    Koehn G, Desai R, Davies E, Forsyth R, Eastwood J, Poedts Set al., 2022,

    Successive interacting coronal mass ejections: How to create a perfect storm?

    , The Astrophysical Journal: an international review of astronomy and astronomical physics, Vol: 941, ISSN: 0004-637X

    Coronal mass ejections (CMEs) are the largest type of eruptions on the Sun and the main driver of severe space weather at the Earth. In this study, we implement a force-free spheromak CME description within 3D magnetohydrodynamic simulations to parametrically evaluate successive interacting CMEs within a representative heliosphere. We explore CME–CME interactions for a range of orientations, launch time variations, and CME handedness and quantify their geo-effectiveness via the primary solar wind variables and empirical measures of the disturbance storm time index and subsolar magnetopause standoff distance. We show how the interaction of two moderate CMEs between the Sun and the Earth can translate into extreme conditions at the Earth and how CME–CME interactions at different radial distances can maximize different solar wind variables that induce different geophysical impacts. In particular, we demonstrate how the orientation and handedness of a given CME can have a significant impact on the conservation and loss of magnetic flux, and consequently Bz, due to magnetic reconnection with the interplanetary magnetic field. This study thus implicates the identification of CME chirality in the solar corona as an early diagnostic for forecasting geomagnetic storms involving multiple CMEs.

  • Journal article
    Page B, Bassett N, Lecacheux A, Pulupa M, Rapetti D, Bale SDet al., 2022,

    The <i>l</i>=2 spherical harmonic expansion coefficients of the sky brightness distribution between 0.5 and 7 MHz

    , ASTRONOMY & ASTROPHYSICS, Vol: 668, ISSN: 0004-6361
  • Journal article
    Paranicas C, Mauk B, Kollmann P, Clark G, Haggerty D, Westlake J, Liuzzo L, Masters A, Cassidy T, Bagenal F, Bolton Set al., 2022,

    Energetic charged particle fluxes relevant to Ganymede's polar region

    , Geophysical Research Letters, Vol: 49, ISSN: 0094-8276

    The JEDI instrument made measurements of energetic charged particles near Ganymede during a close encounter with that moon. Here we find ion flux levels are similar close to Ganymede itself but outside its magnetosphere and on near wake and open field lines. But energetic electron flux levels are more than a factor of 2 lower on polar and near-wake field lines than on nearby Jovian field lines at all energies reported here. Flux levels are relevant to the weathering of the surface, particularly processes that affect the distribution of ice, since surface brightness has been linked to the open-closed field line boundary. For this reason, we estimate the sputtering rates expected in the polar regions due to energetic heavy ions. Other rates, such as those related to radiolysis by plasma and particles that can reach the surface, need to be added to complete the picture of charged particle weathering.

  • Journal article
    Masters A, Ioannou C, Rayns N, 2022,

    Does Uranus’ asymmetric magnetic field produce a relatively weak proton radiation belt?

    , Geophysical Research Letters, Vol: 49, ISSN: 0094-8276

    Since the Voyager 2 flyby in 1986 the radiation belts of Uranus have presented a problem for physicists. The observations indicate the electron radiation belt is far more intense than the proton radiation belt, and while the electron intensities are close to the upper theoretical limit, proton intensities are well below. Here we propose the relatively weak proton radiation belt could be due to Uranus' asymmetric magnetic field. We model test particle motion through the field to show that perturbations arising from asymmetry are greater the larger the particle gyroradius, predominantly affecting urn:x-wiley:00948276:media:grl65197:grl65197-math-0001100-keV protons. For these particles, more rapid changes in maximum distance from the planet during a bounce motion promote trajectory evolution into regions where they could be lost through impact with the rings, impact with the atmosphere, or to the distant magnetosphere and solar wind. We suggest this could explain a relatively weak proton radiation belt at Uranus.

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