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  • Journal article
    Cheng ZW, Shi JK, Torkar K, Lu GP, Dunlop MW, Carr CM, Reme H, Dandouras I, Fazakerley Aet al., 2021,

    Impact of the solar wind dynamic pressure on the field-aligned currents in the magnetotail: cluster observation

    , JGR: Space Physics, Vol: 126, Pages: 1-12, ISSN: 2169-9402

    We statistically investigate the influence of the solar wind dynamic pressure (SW Pdyn) on the field-aligned currents (FACs) in the magnetotail with 1,492 FAC cases from July to October in 2001 and 2004, which covers 74 Cluster crossings of the plasma sheet boundary layer (PSBL) in both storm time and non-storm time. The FAC density in the magnetotail is derived from the magnetic field data with the four-point measurement of Cluster, and the SW Pdyn is taken from ACE data. The results indicate the FAC density becomes stronger with increasing SW Pdyn. The statistics show that the FAC occurrence increased monotonically with SW Pdyn in the three levels (Weak: SW Pdyn < 2 nPa; Medium: 2 nPa ≤ SW Pdyn ≤ 5 nPa; Strong: SW Pdyn > 5 nPa). The FAC density increased with increasing SW Pdyn, while its footprint (invariant latitude, ILAT) in the polar region decreased with increasing SW Pdyn. The response of the FAC to SW Pdyn in the magnetotail had a north-south hemispheric asymmetry. The FAC density had a better correlation with SW Pdyn in the Northern hemisphere, while the footprint had a better correlation with SW Pdyn in the Southern hemisphere. Possible underlying mechanisms for our results are analyzed and discussed. However, it requires more observations and simulation studies to find out the mechanism of north-south asymmetry.
  • Journal article
    Kieokaew R, Lavraud B, Yang Y, Matthaeus WH, Ruffolo D, Stawarz JE, Aizawa S, Foullon C, Génot V, Pinto RF, Fargette N, Louarn P, Rouillard A, Fedorov A, Penou E, Owen CJ, Horbury T, O'Brien H, Evans V, Angelini Vet al., 2021,

    Solar Orbiter observations of the Kelvin-Helmholtz waves in the solar wind

    , Astronomy and Astrophysics: a European journal, Vol: 656, ISSN: 0004-6361

    Context. The Kelvin-HeImholtz (KH) instability is a nonlinear shear-driven instability that develops at the interface between shear flows in plasmas. KH waves have been inferred in various astrophysical plasmas, and have been observed in situ at the magnetospheric boundaries of solar-system planets and through remote sensing at the boundaries of coronal mass ejections.Aims. KH waves are also expected to develop at flow shear interfaces in the solar wind. While they were hypothesized to play an important role in the mixing of plasmas and in triggering solar wind fluctuations, their direct and unambiguous observation in the solar wind was still lacking.Methods. We report in situ observations of quasi-periodic magnetic and velocity field variations plausibly associated with KH waves using Solar Orbiter during its cruise phase. They are found in a shear layer in the slow solar wind in the close vicinity of the heliospheric current sheet. An analysis was performed to derive the local configuration of the waves. A 2D magnetohydrodynamics simulation was also set up with approximate empirical values to test the stability of the shear layer. In addition, magnetic spectra of the event were analyzed.Results. We find that the observed conditions satisfy the KH instability onset criterion from the linear theory analysis, and its development is further confirmed by the simulation. The current sheet geometry analyses are found to be consistent with KH wave development, albeit with some limitations likely owing to the complex 3D nature of the event and solar wind propagation. Additionally, we report observations of an ion jet consistent with magnetic reconnection at a compressed current sheet within the KH wave interval. The KH activity is found to excite magnetic and velocity fluctuations with power law scalings that approximately follow k−5/3 and k−2.8 in the inertial and dissipation ranges, respectively. Finally, we discuss reasons for the lack of in situ KH wave det
  • Journal article
    Matteini L, Laker R, Horbury T, Woodham L, Bale SD, Stawarz JE, Woolley T, Steinvall K, Jones GH, Grant SR, Afghan Q, Galand M, O'Brien H, Evans V, Angelini V, Maksimovic M, Chust T, Khotyaintsev Y, Krasnoselskikh V, Kretzschmar M, Lorfevre E, Plettemeier D, Soucek J, Steller M, Stverak S, Travnicek P, Vaivads A, Vecchio A, Wimmer-Schweingruber RF, Ho GC, Gomez-Herrero R, Rodriguez-Pacheco J, Louarn P, Fedorov A, Owen CJ, Bruno R, Livi S, Zouganelis I, Muller Det al., 2021,

    Solar Orbiter's encounter with the tail of comet C/2019 Y4 (ATLAS): Magnetic field draping and cometary pick-up ion waves

    , Astronomy and Astrophysics: a European journal, Vol: 656, ISSN: 0004-6361

    ontext. Solar Orbiter is expected to have flown close to the tail of comet C/2019 Y4 (ATLAS) during the spacecraft’s first perihelion in June 2020. Models predict a possible crossing of the comet tails by the spacecraft at a distance from the Sun of approximately 0.5 AU.Aims. This study is aimed at identifying possible signatures of the interaction of the solar wind plasma with material released by comet ATLAS, including the detection of draped magnetic field as well as the presence of cometary pick-up ions and of ion-scale waves excited by associated instabilities. This encounter provides us with the first opportunity of addressing such dynamics in the inner Heliosphere and improving our understanding of the plasma interaction between comets and the solar wind.Methods. We analysed data from all in situ instruments on board Solar Orbiter and compared their independent measurements in order to identify and characterize the nature of structures and waves observed in the plasma when the encounter was predicted.Results. We identified a magnetic field structure observed at the start of 4 June, associated with a full magnetic reversal, a local deceleration of the flow and large plasma density, and enhanced dust and energetic ions events. The cross-comparison of all these observations support a possible cometary origin for this structure and suggests the presence of magnetic field draping around some low-field and high-density object. Inside and around this large scale structure, several ion-scale wave-forms are detected that are consistent with small-scale waves and structures generated by cometary pick-up ion instabilities.Conclusions. Solar Orbiter measurements are consistent with the crossing through a magnetic and plasma structure of cometary origin embedded in the ambient solar wind. We suggest that this corresponds to the magnetotail of one of the fragments of comet ATLAS or to a portion of the tail that was previously disconnected and advected past the spacec
  • Journal article
    Oieroset M, Phan TD, Ergun R, Ahmadi N, Genestreti K, Drake JF, Liu Y-H, Haggerty C, Eastwood JP, Shay MA, Pyakurel PS, Haaland S, Oka M, Goodbred M, Eriksson S, Burch JL, Torbert RB, Khotyaintsev Y, Russell CT, Strangeway RJ, Gershman DJ, Giles BLet al., 2021,

    Spatial evolution of magnetic reconnection diffusion region structures with distance from the X-line

    , Physics of Plasmas, Vol: 28, ISSN: 1070-664X

    We report Magnetospheric Multiscale four-spacecraft observations of a thin reconnecting current sheet with weakly asymmetric inflow conditions and a guide field of approximately twice the reconnecting magnetic field. The event was observed at the interface of interlinked magnetic field lines at the flank magnetopause when the maximum spacecraft separation was 370 km and the spacecraft covered ∼1.7 ion inertial lengths (di) in the reconnection outflow direction. The ion-scale spacecraft separation made it possible to observe the transition from electron-only super ion-Alfvénic outflow near the electron diffusion region (EDR) to the emergence of sub-Alfvénic ion outflow in the ion diffusion region (IDR). The EDR to IDR evolution over a distance less than 2 di also shows the transition from a near-linear reconnecting magnetic field reversal to a more bifurcated current sheet as well as significant decreases in the parallel electric field and dissipation. Both the ion and electron heating in this diffusion region event were similar to the previously reported heating in the far downstream exhausts. The dimensionless reconnection rate, obtained four different ways, was in the range of 0.13–0.27. This event reveals the rapid spatial evolution of the plasma and electromagnetic fields through the EDR to IDR transition region
  • Journal article
    Graven H, Lamb E, Blake D, Khatiwala Set al., 2021,

    Future changes in δ 13 C of dissolved inorganic carbon in the ocean

    , Earth's Future, Vol: 9, Pages: 1-12, ISSN: 2328-4277

    Emissions of carbon dioxide from fossil fuel combustion are reducing the ratio 13C/12C, δ13C, in atmospheric urn:x-wiley:23284277:media:eft2900:eft2900-math-0001 and in the carbon in the ocean and terrestrial biosphere that exchanges with the atmosphere on timescales of decades to centuries. Future changes to fossil fuel emissions vary across different scenarios and may cause decreases of more than 6‰ in atmospheric δ13urn:x-wiley:23284277:media:eft2900:eft2900-math-0002 between 1850 and 2100. The effects of these potential changes on the three-dimensional distribution of δ13C in the ocean has not yet been investigated. Here, we use an ocean biogeochemical-circulation model forced with a range of Shared Socioeconomic Pathway (SSP)-based scenarios to simulate δ13C in ocean dissolved inorganic carbon from 1850 to 2100. In the future, vertical δ13C gradients characteristic of the biological pump are reduced or reversed, relative to the preindustrial period, with the reversal occurring in higher emission scenarios. For the highest emission scenario, SSP5-8.5, surface δ13C in the centre of Pacific subtropical gyres falls from 2.2‰ in 1850 to -3.5‰ by 2100. In lower emission scenarios, δ13C in the surface ocean decreases but then rebounds. The relationship between anthropogenic carbon (Cant) and δ13C in the ocean shows a larger scatter in all scenarios, suggesting that errors in δ13C-based estimates of Cant may increase in the future. These simulations were run with fixed physical forcing and ocean circulation, providing a baseline of predicted δ13C. Further work is needed to investigate the impact of climate-carbon cycle feedbacks on ocean δ13C changes.
  • Journal article
    Zhao L-L, Zank GP, He JS, Telloni D, Adhikari L, Nakanotani M, Kasper JC, Bale SDet al., 2021,

    MHD and Ion Kinetic Waves in Field-aligned Flows Observed by Parker Solar Probe

    , ASTROPHYSICAL JOURNAL, Vol: 922, ISSN: 0004-637X
  • Journal article
    Tao J, Wang L, Li G, Wimmer-Schweingruber RF, Salem C, Jian LK, Bale SDet al., 2021,

    Solar Wind ∼0.15-1.5 keV Electrons around Corotating Interaction Regions at 1 au

    , ASTROPHYSICAL JOURNAL, Vol: 922, ISSN: 0004-637X
  • Journal article
    Pitna A, Safrankova J, Nemecek Z, Franci L, Pi Get al., 2021,

    A Novel Method for Estimating the Intrinsic Magnetic Field Spectrum of Kinetic-Range Turbulence

    , ATMOSPHERE, Vol: 12
  • Journal article
    Davies EE, Forsyth RJ, Winslow RM, Moestl C, Lugaz Net al., 2021,

    A Catalog of Interplanetary Coronal Mass Ejections Observed by Juno between 1 and 5.4 au

    , ASTROPHYSICAL JOURNAL, Vol: 923, ISSN: 0004-637X
  • Journal article
    Lai T-K, Hendricks EA, Yau MK, 2021,

    Long-Term Effect of Barotropic Instability across the Moat in Double-Eyewall Tropical Cyclone–Like Vortices in Forced and Unforced Shallow-Water Models

    , Journal of the Atmospheric Sciences, Vol: 78, Pages: 4103-4126, ISSN: 0022-4928

    <jats:title>Abstract</jats:title><jats:p>Secondary eyewall formation and the ensuing eyewall replacement cycles may take place in mature tropical cyclones (TCs) during part of their lifetime. A better understanding of the underlying dynamics is beneficial to improving the prediction of TC intensity and structure. Previous studies suggested that the barotropic instability (BI) across the moat (aka type-2 BI) can make a substantial contribution to the inner-eyewall decay through the associated eddy radial transport of absolute angular momentum (AAM). Simultaneously, the type-2 BI can also increase the AAM of the outer eyewall. While the previous studies focused on the early stage of the type-2 BI, this paper explores the long-term effect of the type-2 BI and the underlying processes in forced and unforced shallow-water experiments. Under the long-term effect, it will be shown that the inner eyewalls repeatedly weaken and strengthen (while the order is reversed for the outer eyewalls). Sensitivity tests are conducted to examine the sensitivity of the long-term effect of the type-2 BI to different vortex parameters and the strength of the parameterized diabatic heating. Implication of the long-term effect for the intensity changes of the inner and outer eyewalls of real TCs are also discussed.</jats:p>
  • Journal article
    Vasko IY, Alimov K, Phan TD, Bale SD, Mozer FS, Artemyev Aet al., 2021,

    Kinetic-scale Current Sheets in the Solar Wind at 1 au: Properties and the Necessary Condition for Reconnection

    , ASTROPHYSICAL JOURNAL LETTERS, Vol: 923, ISSN: 2041-8205
  • Journal article
    Pecora F, Servidio S, Greco A, Matthaeus WH, McComas DJ, Giacalone J, Joyce CJ, Getachew T, Cohen CMS, Leske RA, Wiedenbeck ME, McNutt RL, Hill ME, Mitchell DG, Christian ER, Roelof EC, Schwadron NA, Bale SDet al., 2021,

    Parker Solar Probe observations of helical structures as boundaries for energetic particles

    , MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 508, Pages: 2114-2122, ISSN: 0035-8711
  • Journal article
    Papini E, Hellinger P, Verdini A, Landi S, Franci L, Montagud-Camps V, Matteini Let al., 2021,

    Properties of Hall-MHD Turbulence at Sub-Ion Scales: Spectral Transfer Analysis

    , ATMOSPHERE, Vol: 12
  • Journal article
    Ala-Lahti M, Dimmock AP, Pulkkinen T, Good SW, Yordanova E, Turc L, Kilpua EKJet al., 2021,

    Transmission of an ICME Sheath Into the Earth's Magnetosheath and the Occurrence of Traveling Foreshocks

    , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 126, ISSN: 2169-9380
  • Journal article
    Ceppi P, Fueglistaler S, 2021,

    The El Niño–Southern Oscillation pattern effect

    , Geophysical Research Letters, Vol: 48, Pages: 1-9, ISSN: 0094-8276

    El Niño–Southern Oscillation (ENSO) variability is accompanied by out-of-phase anomalies in the top-of-atmosphere tropical radiation budget, with anomalous downward flux (i.e., net radiative heating) before El Niño and anomalous upward flux thereafter (and vice versa for La Niña). Here, we show that these radiative anomalies result mainly from a sea surface temperature (SST) “pattern effect,” mediated by changes in tropical-mean tropospheric stability. These stability changes are caused by SST anomalies migrating from climatologically cool to warm regions over the ENSO cycle. Our results are suggestive of a two-way coupling between SST variability and radiation, where ENSO-induced radiative changes may in turn feed back onto SST during ENSO.
  • Journal article
    Stephan K, Roatsch T, Tosi F, Matz K-D, Kersten E, Wagner R, Molyneux P, Palumbo P, Poulet F, Hussmann H, Barabash S, Bruzzone L, Dougherty M, Gladstone R, Gurvits LI, Hartogh P, Iess L, Wahlund J-E, Wurz P, Witasse O, Grasset O, Altobelli N, Carter J, Cavalie T, d'Aversa E, Della Corte V, Filacchione G, Galli A, Galluzzi V, Gwinner K, Hauber E, Jaumann R, Krohn K, Langevin Y, Lucchetti A, Migliorini A, Piccioni G, Solomonidou A, Stark A, Tobie G, Tubiana C, Vallat C, Van Hoolst Tet al., 2021,

    Regions of interest on Ganymede's and Callisto's surfaces as potential targets for ESA's JUICE mission

    , PLANETARY AND SPACE SCIENCE, Vol: 208, ISSN: 0032-0633
  • Journal article
    Dunlop MW, Dong XC, Wang TY, Eastwood JP, Robert P, Haaland S, Yang YY, Escoubet P, Rong ZJ, Shen C, Fu HS, De Keyser Jet al., 2021,

    Curlometer technique and applications

    , Journal of Geophysical Research: Space Physics, Vol: 126, Pages: 1-29, ISSN: 2169-9380

    We review the range of applications and use of the curlometer, initially developed to analyze Cluster multi-spacecraft magnetic field data; but more recently adapted to other arrays of spacecraft flying in formation, such as MMS small-scale, 4-spacecraft configurations; THEMIS close constellations of 3–5 spacecraft, and Swarm 2–3 spacecraft configurations. Although magnetic gradients require knowledge of spacecraft separations and the magnetic field, the structure of the electric current density (for example, its relative spatial scale), and any temporal evolution, limits measurement accuracy. Nevertheless, in many magnetospheric regions the curlometer is reliable (within certain limits), particularly under conditions of time stationarity, or with supporting information on morphology (for example, when the geometry of the large scale structure is expected). A number of large-scale regions have been covered, such as: the cross-tail current sheet, ring current, the current layer at the magnetopause and field-aligned currents. Transient and smaller scale current structures (e.g., reconnected flux tube or dipolarisation fronts) and energy transfer processes. The method is able to provide estimates of single components of the vector current density, even if there are only two or three satellites flying in formation, within the current region, as can be the case when there is a highly irregular spacecraft configuration. The computation of magnetic field gradients and topology in general includes magnetic rotation analysis and various least squares approaches, as well as the curlometer, and indeed the added inclusion of plasma measurements and the extension to larger arrays of spacecraft have recently been considered.
  • Journal article
    Woolley T, Matteini L, McManus MD, Bercic L, Badman ST, Woodham LD, Horbury TS, Bale SD, Laker R, Stawarz JE, Larson DEet al., 2021,

    Plasma properties, switchback patches, and low alpha-particle abundance in slow Alfvenic coronal hole wind at 0.13 au

    , MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 508, Pages: 236-244, ISSN: 0035-8711

    The Parker Solar Probe (PSP) mission presents a unique opportunity to study the near-Sun solar wind closer than any previous spacecraft. During its fourth and fifth solar encounters, PSP had the same orbital trajectory, meaning that solar wind was measured at the same latitudes and radial distances. We identify two streams measured at the same heliocentric distance (∼0.13 au) and latitude (∼–3∘.5⁠) across these encounters to reduce spatial evolution effects. By comparing the plasma of each stream, we confirm that they are not dominated by variable transient events, despite PSP’s proximity to the heliospheric current sheet. Both streams are consistent with a previous slow Alfvénic solar wind study once radial effects are considered, and appear to originate at the Southern polar coronal hole boundary. We also show that the switchback properties are not distinctly different between these two streams. Low α-particle abundance (∼0.6 per cent) is observed in the encounter 5 stream, suggesting that some physical mechanism must act on coronal hole boundary wind to cause α-particle depletion. Possible explanations for our observations are discussed, but it remains unclear whether the depletion occurs during the release or the acceleration of the wind. Using a flux tube argument, we note that an α-particle abundance of ∼0.6 per cent in this low-velocity wind could correspond to an abundance of ∼0.9 per cent at 1 au. Finally, as the two streams roughly correspond to the spatial extent of a switchback patch, we suggest that patches are distinct features of coronal hole wind.
  • Journal article
    Chakravorty S, Perez RC, Anderson BT, Larson SM, Giese BS, Pivotti Vet al., 2021,

    Ocean Dynamics are Key to Extratropical Forcing of El Niño

    , Journal of Climate, Vol: 34, Pages: 8739-8753, ISSN: 0894-8755

    <jats:title>Abstract</jats:title><jats:p>El Niño–Southern Oscillation (ENSO) has been recently linked with extratropical Pacific Ocean atmospheric variability. The two key mechanisms connecting the atmospheric variability of the extratropical Pacific with ENSO are the heat flux–driven “seasonal footprinting mechanism” (SFM) and the ocean dynamics–driven “trade wind charging” (TWC) mechanism. However, their relative contributions to ENSO are still unknown. Here we present modeling evidence that the positive phase of the SFM generates a weaker, short-lived central Pacific El Niño–like warming pattern in the autumn, whereas the TWC positive phase leads to a wintertime eastern Pacific El Niño–like warming. When both mechanisms are active, a strong, persistent El Niño develops. While both mechanisms can trigger equatorial wind anomalies that generate an El Niño, the strength and persistence of the warming depends on the subsurface heat content buildup by the TWC mechanism. These results suggest that while dynamical coupling associated with extratropical forcing is crucial to maintain an El Niño, thermodynamical coupling is an extratropical source of El Niño diversity.</jats:p>
  • Journal article
    Chakravorty S, Perez RC, Gnanaseelan C, Anderson BTet al., 2021,

    Revisiting the Recharge and Discharge Processes for Different Flavors of El Niño

    , Journal of Geophysical Research: Oceans, Vol: 126, ISSN: 2169-9275

    <jats:title>Abstract</jats:title><jats:p>El Niño‐related sea surface temperature (SST) anomalies over the tropical Pacific Ocean impact global climates, but these impacts differ substantially for conventional cold tongue El Niño (CT El Niño) and the central Pacific El Niño (CP El Niño) events. This study is motivated by the need for a better understanding of the recharge/discharge processes associated with these two different flavors of El Niño. Composite analysis based on improved CT and CP El Niño identification methods applied to the Simple Ocean Data Assimilation demonstrates that the recharge/discharge processes are active during CT El Niño events. In contrast, for CP El Niño events, the recharge/discharge processes do not play a significant role. Prior to a CT El Niño, warm water accumulates over the western Pacific due to off‐equatorial anticyclonic wind stress curl. The onset of a CT El Niño is closely associated with the formation of a cyclonic atmospheric circulation over the northwest Pacific in the winter and spring, which induces westerly wind anomalies in the equatorial western Pacific and initiates eastward warm water transport. This leads to peak warming in the eastern equatorial Pacific the following winter, followed by the poleward discharge of warm water. This quasi‐cyclical behavior provides a measure of predictability. In contrast, the CP El Niño events do not show a precursor subsurface warming signal along the tropical Pacific thermocline. Instead, modest warm SST anomalies appear in boreal summer and peak in the fall, with weak subsurface warming mainly in the fall during CP El Niños. Hence, CP El Niños are less predictable in terms of an equatorial thermocline precursor than CT El Niño events.</jats:p>
  • Journal article
    Bergman S, Wieser GS, Wieser M, Nilsson H, Vigren E, Beth A, Masunaga K, Eriksson Aet al., 2021,

    Flow directions of low-energy ions in and around the diamagnetic cavity of comet 67P

    , Monthly Notices of the Royal Astronomical Society, Vol: 507, Pages: 4900-4913, ISSN: 0035-8711

    The flow direction of low-energy ions around comet 67P/Churyumov–Gerasimenko has previously been difficult to constrain due to the influence of the spacecraft potential. The Ion Composition Analyzer of the Rosetta Plasma Consortium (RPC-ICA) on Rosetta measured the distribution function of positive ions with energies down to just a few eV/q throughout the escort phase of the mission. Unfortunately, the substantial negative spacecraft potential distorted the directional information of the low-energy data. In this work, we present the flow directions of low-energy ions around comet 67P, corrected for the spacecraft potential using Particle-In-Cell simulation results. We focus on the region in and around the diamagnetic cavity, where low-energy ions are especially important for the dynamics. We separate between slightly accelerated ‘burst’ features and a more constant ‘band’ of low-energy ions visible in the data. The ‘bursts’ are flowing radially outwards from the nucleus with an antisunward component while the ‘band’ is predominantly streaming back towards the comet. This provides evidence of counter-streaming ions, which has implications for the overall expansion velocity of the ions. The backstreaming ions are present also at times when the diamagnetic cavity was not detected, indicating that the process accelerating the ions back towards the comet is not connected to the cavity boundary.
  • Journal article
    Palmerio, Nieves-Chinchilla, Kilpua, Barnes D, Zhukov, Jian, Witasse, Provan, Tao, Lamy, Bradley, Mays, Mostl, Roussos, Futaana, Masters A, Sanchez-Canoet al., 2021,

    Magnetic structure and propagation of two interacting CMEs from the Sun to Saturn

    , Journal of Geophysical Research: Space Physics, Vol: 126, Pages: 1-28, ISSN: 2169-9380

    One of the grand challenges in heliophysics is the characterization of coronal mass ejection (CME) magnetic structure and evolution from eruption at the Sun through heliospheric propagation. At present, the main difficulties are related to the lack of direct measurements of the coronal magnetic fields and the lack of 3D in-situ measurements of the CME body in interplanetary space. Nevertheless, the evolution of a CME magnetic structure can be followed using a combination of multi-point remote-sensing observations and multi-spacecraft in-situ measurements as well as modeling. Accordingly, we present in this work the analysis of two CMEs that erupted from the Sun on April 28, 2012. We follow their eruption and early evolution using remote-sensing data, finding indications of CME–CME interaction, and then analyze their interplanetary counterpart(s) using in-situ measurements at Venus, Earth, and Saturn. We observe a seemingly single flux rope at all locations, but find possible signatures of interaction at Earth, where high-cadence plasma data are available. Reconstructions of the in-situ flux ropes provide almost identical results at Venus and Earth but show greater discrepancies at Saturn, suggesting that the CME was highly distorted and/or that further interaction with nearby solar wind structures took place before 10 AU. This work highlights the difficulties in connecting structures from the Sun to the outer heliosphere and demonstrates the importance of multi-spacecraft studies to achieve a deeper understanding of the magnetic configuration of CMEs.
  • Journal article
    Mejnertsen L, Eastwood J, Chittenden J, 2021,

    Control of magnetopause flux rope topology by non-local reconnection

    , Frontiers in Astronomy and Space Sciences, Vol: 8, Pages: 1-15, ISSN: 2296-987X

    Dayside magnetic reconnection between the interplanetary magnetic field and the Earth’s magnetic field is the primary mechanism enabling mass and energy entry into the magnetosphere. During favorable solar wind conditions, multiple reconnection X-lines can form on the dayside magnetopause, potentially forming flux ropes. These flux ropes move tailward, but their evolution and fate in the tail is not fully understood. Whilst flux ropes may constitute a class of flux transfer events, the extent to which they add flux to the tail depends on their topology, which can only be measured in situ by satellites providing local observations. Global simulations allow the entire magnetospheric system to be captured at an instant in time, and thus reveal the interconnection between different plasma regions and dynamics on large scales. Using the Gorgon MHD code, we analyze the formation and evolution of flux ropes on the dayside magnetopause during a simulation of a real solar wind event. With a relatively strong solar wind dynamic pressure and southward interplanetary magnetic field, the dayside region becomes very dynamic with evidence of multiple reconnection events. The resulting flux ropes transit around the flank of the magnetosphere before eventually dissipating due to non-local reconnection. This shows that non-local effects may be important in controlling the topology of flux ropes and is a complicating factor in attempts to establish the overall contribution that flux ropes make in the general circulation of magnetic flux through the magnetosphere.
  • Journal article
    Gurnett DA, Kurth WS, Burlaga LF, Berdichevsky DB, Pogorelov N, Pulupa M, Bale SDet al., 2021,

    Origin of the Weak Plasma Emission Line Detected by Voyager 1 in the Interstellar Medium: Evidence for Suprathermal Electrons

    , ASTROPHYSICAL JOURNAL, Vol: 921, ISSN: 0004-637X
  • Journal article
    Giacalone J, Burgess D, Bale SD, Desai M, Mitchell JG, Lario D, Chen CHK, Christian ER, de Nolfo GA, Hill ME, Matthaeus WH, McComas DJ, McNutt RL, Mitchell DG, Roelof EC, Schwadron NA, Getachew T, Joyce CJet al., 2021,

    Energetic Particles Associated with a Coronal Mass Ejection Shock Interacting with a Convected Magnetic Structure

    , ASTROPHYSICAL JOURNAL, Vol: 921, ISSN: 0004-637X
  • Journal article
    Vech D, Malaspina DM, Cattell C, Schwartz SJ, Ergun RE, Klein KG, Kromyda L, Chasapis Aet al., 2021,

    Experimental Determination of Ion Acoustic Wave Dispersion Relation With Interferometric Analysis

    , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 126, ISSN: 2169-9380
  • Journal article
    Lai, Jia, Russell, Jia X, Masters A, Dougherty M, Cuiet al., 2021,

    Magnetic flux circulation in the Saturnian magnetosphere as constrained by Cassini observations in the inner magnetosphere

    , Journal of Geophysical Research: Space Physics, Vol: 126, Pages: 1-9, ISSN: 2169-9380

    In steady state, magnetic flux conservation must be maintained in Saturn’s magnetosphere. The Enceladus plumes add mass to magnetic flux tubes in the inner magnetosphere, and centrifugal force pulls the mass-loaded flux tubes outward. Those flux tubes are carried outward to the magnetotail where they deposit their mass and return to the mass loading region. It may take days for the magnetic flux to be carried outward to the tail, but the return of the nearly empty flux tubes can last only several hours, with speeds of inward motion around 200 km/s. Using time sequences of Cassini particle count rate, the difference in curvature drift and gradient drift is accounted for to determine the return speed, age, and starting dipole L-shell of return flux tubes. Determination of this flux-return process improves our understanding of the magnetic flux circulation at Saturn and provides insight into how other giant planets remove the mass added by their moons.
  • Journal article
    Bercic L, Maksimovic M, Halekas JS, Landi S, Owen CJ, Verscharen D, Larson D, Whittlesey P, Badman ST, Bale SD, Case AW, Goetz K, Harvey PR, Kasper JC, Korreck KE, Livi R, MacDowall RJ, Malaspina DM, Pulupa M, Stevens MLet al., 2021,

    Ambipolar Electric Field and Potential in the Solar Wind Estimated from Electron Velocity Distribution Functions

    , ASTROPHYSICAL JOURNAL, Vol: 921, ISSN: 0004-637X
  • Journal article
    Teixeira JC, Folberth GA, O'Connor FM, Unger N, Voulgarakis Aet al., 2021,

    Coupling interactive fire with atmospheric composition and climate in the UK Earth System Model

    , Geoscientific Model Development, Vol: 14, Pages: 6515-6539, ISSN: 1991-959X

    Fire constitutes a key process in the Earth system (ES), being driven by climate as well as affecting the climate by changing atmospheric composition and impacting the terrestrial carbon cycle. However, studies on the effects of fires on atmospheric composition, radiative forcing and climate have been limited to date, as the current generation of ES models (ESMs) does not include fully atmosphere–composition–vegetation coupled fires feedbacks. The aim of this work is to develop and evaluate a fully coupled fire–composition–climate ES model. For this, the INteractive Fires and Emissions algoRithm for Natural envirOnments (INFERNO) fire model is coupled to the atmosphere-only configuration of the UK's Earth System Model (UKESM1). This fire–atmosphere interaction through atmospheric chemistry and aerosols allows for fire emissions to influence radiation, clouds and generally weather, which can consequently influence the meteorological drivers of fire. Additionally, INFERNO is updated based on recent developments in the literature to improve the representation of human and/or economic factors in the anthropogenic ignition and suppression of fire. This work presents an assessment of the effects of interactive fire coupling on atmospheric composition and climate compared to the standard UKESM1 configuration that uses prescribed fire emissions. Results show a similar performance when using the fire–atmosphere coupling (the “online” version of the model) when compared to the offline UKESM1 that uses prescribed fire. The model can reproduce observed present-day global fire emissions of carbon monoxide (CO) and aerosols, despite underestimating the global average burnt area. However, at a regional scale, there is an overestimation of fire emissions over Africa due to the misrepresentation of the underlying vegetation types and an underestimation over equatorial Asia due to a lack of representation of peat fires. Despite this, co
  • Journal article
    Maksimovic M, Bale SD, Chust T, Khotyaintsev Y, Krasnoselskikh V, Kretzschmar M, Plettemeier D, Rucker HO, Soucek J, Steller M, Stverak S, Travnicek P, Vaivads A, Chaintreuil S, Dekkali M, Alexandrova O, Astier P-A, Barbary G, Berard D, Bonnin X, Boughedada K, Cecconi B, Chapron F, Chariet M, Collin C, de Conchy Y, Dias D, Gueguen L, Lamy L, Leray V, Lion S, Malac-Allain LR, Matteini L, Nguyen QN, Pantellini F, Parisot J, Plasson P, Thijs S, Vecchio A, Fratter I, Bellouard E, Lorfevre E, Danto P, Julien S, Guilhem E, Fiachetti C, Sanisidro J, Laffaye C, Gonzalez F, Pontet B, Queruel N, Jannet G, Fergeau P, Brochot J-Y, Cassam-Chenai G, Dudok de Wit T, Timofeeva M, Vincent T, Agrapart C, Delory GT, Turin P, Jeandet A, Leroy P, Pellion J-C, Bouzid V, Katra B, Piberne R, Recart W, Santolik O, Kolmasova I, Krupar V, Kruparova O, Pisa D, Uhlir L, Lan R, Base J, Ahlen L, Andre M, Bylander L, Cripps V, Cully C, Eriksson A, Jansson S-E, Johansson EPG, Karlsson T, Puccio W, Brinek J, ottacher H, Panchenko M, Berthomier M, Goetz K, Hellinger P, Horbury TS, Issautier K, Kontar E, Krucker S, Le Contel O, Louarn P, Martinovic M, Owen CJ, Retino A, Rodriguez-Pacheco J, Sahraoui F, Wimmer-Schweingruber RF, Zaslavsky A, Zouganelis Iet al., 2021,

    The Solar Orbiter Radio and Plasma Waves (RPW) instrument (vol 642, A12, 2020)

    , ASTRONOMY & ASTROPHYSICS, Vol: 654, ISSN: 0004-6361

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