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  • Journal article
    Akhavan-Tafti M, Kasper J, Huang J, Bale Set al., 2021,

    Discontinuity analysis of the leading switchback transition regions

    , ASTRONOMY & ASTROPHYSICS, Vol: 650, ISSN: 0004-6361
  • Journal article
    Cattell C, Short B, Breneman A, Halekas J, Whittesley P, Larson D, Kasper JC, Stevens M, Case T, Moncuquet M, Bale S, Bonnell J, de Wit TD, Goetz K, Harvey P, MacDowall R, Malaspina D, Maksimovic M, Pulupa M, Goodrich Ket al., 2021,

    Narrowband oblique whistler-mode waves: comparing properties observed by Parker Solar Probe at <0.3 AU and STEREO at 1 AU

    , ASTRONOMY & ASTROPHYSICS, Vol: 650, ISSN: 0004-6361
  • Journal article
    Finley AJ, McManus MD, Matt SP, Kasper JC, Korreck KE, Case AW, Stevens ML, Whittlesey P, Larson D, Livi R, Bale SD, de Wit TD, Goetz K, Harvey PR, MacDowall RJ, Malaspina DM, Pulupa Met al., 2021,

    The contribution of alpha particles to the solar wind angular momentum flux in the inner heliosphere

    , ASTRONOMY & ASTROPHYSICS, Vol: 650, ISSN: 0004-6361
  • Journal article
    Harra L, Brooks DH, Bale SD, Mandrini CH, Barczynski K, Sharma R, Badman ST, Dominguez SV, Pulupa Met al., 2021,

    The active region source of a type III radio storm observed by Parker Solar Probe during encounter 2

    , ASTRONOMY & ASTROPHYSICS, Vol: 650, ISSN: 0004-6361
  • Journal article
    Schwadron NA, Joyce CJ, Aly A, Cohen CMS, Desai M, McComas DJ, Niehof JT, Mobius E, Lee M, Bower J, Bale S, Case A, Christian ER, Davis AJ, de Wet W, Goetz K, Giacalone J, Hill ME, Allen R, Kasper JC, Korreck K, Leske RA, Malandraki O, Matthaeus WH, McNutt RL, Mewaldt RA, Mitchell DG, Pulupa M, Rankin JS, Roelof EC, Stone EC, Szalay JR, Wiedenbeck MEet al., 2021,

    A new view of energetic particles from stream interaction regions observed by Parker Solar Probe

    , ASTRONOMY & ASTROPHYSICS, Vol: 650, ISSN: 0004-6361
  • Journal article
    Quaas J, Gryspeerdt E, Vautard R, Boucher Oet al., 2021,

    Climate impact of aircraft-induced cirrus assessed from satellite observations before and during COVID-19

    , Environmental Research Letters, Vol: 16, Pages: 1-6, ISSN: 1748-9326

    Aircraft produce condensation trails, which are thought to increase high-level cloudiness under certain conditions. Howeverthe magnitude of such an effect and whether this contributes substantially to the radiative forcing due to the aviation sectorremain uncertain. The very substantial, near-global reduction in air traffic in response to the COVID-19 outbreak offers anunprecedented opportunity to identify the anthropogenic contribution to the observed cirrus coverage and thickness. Here weshow, using an analysis of satellite observations for the period March-May 2020, that in the 20% of the Northern Hemispheremid-latitudes with the largest air traffic reduction, cirrus fraction was reduced by ~9 ± 1.5% on average, and cirrus emissivitywas reduced by ~2 ±5% relative to what they should have been with normal air traffic. The changes are corroborated by aconsistent estimate based on linear trends over the period 2011 – 2019. The change in cirrus translates to a global radiativeforcing of 61 ±39 mWm-2. This estimate is somewhat smaller than previous assessments.
  • Journal article
    Phan TD, Lavraud B S J, Halekas, Øieroset M, Drake JF, Eastwood JP, Shay MA, Bale SD, Larson D, Livi R, Whittlesey PL, Rahmati A, Pulupa M, McManus MD, Verniero JL, Bonnell JW, Stevens M, Case AWet al., 2021,

    Prevalence of magnetic reconnection in the near-Sun heliospheric current sheet

    , Astronomy & Astrophysics, Vol: 650, Pages: 1-14, ISSN: 0004-6361

    During three of its first five orbits around the Sun, Parker Solar Probe (PSP) crossed the large-scale Heliospheric Current Sheet (HCS)multiple times and provided unprecedented detailed plasma and field observations of the near-Sun HCS. We report the commondetections by PSP of reconnection exhaust signatures in the HCS at heliocentric distances of 29.5-107 solar radii during Encounters1, 4 and 5. Both sunward and antisunward-directed reconnection exhausts were observed. In the sunward reconnection exhausts,PSP detected counterstreaming strahl electrons, indicating that HCS reconnection resulted in the formation of closed magnetic fieldlines with both ends connected to the Sun. In the antisunward exhausts, PSP observed dropouts of strahl electrons, consistent withthe reconnected HCS field lines being disconnected from the Sun. The common detection of reconnection in the HCS suggests thatreconnection is almost always active in the HCS near the Sun. Furthermore, the occurrence of multiple long-duration partial crossingsof the HCS suggests that HCS reconnection could produce chains of large bulges with spatial dimensions of up to several solarradii. The finding of the prevalence of reconnection in the HCS is somewhat surprising since PSP has revealed that the HCS is muchthicker than the kinetic scales required for reconnection onset. The observations are also in stark contrast with the apparent absenceof reconnection in most of the small-scale and much more intense current sheets encountered near perihelia, many of which areassociated with ‘switchbacks’. Thus, the PSP findings suggest that large-scale dynamics either locally in the solar wind or within thecoronal source of the HCS (at the tip of helmet streamers) plays a critical role in triggering reconnection onset.
  • Journal article
    Fargette N, Lavraud B, Rouillard A, Eastwood JP, Bale SD, Phan T, Øieroset M, Halekas JS, Kasper J, Berthomier M, Case AW, Korreck KE, Larson DE, Louarn P, Malaspina D, Pulupa M, Stevens ML, Whittlesey PLet al., 2021,

    Magnetic increases with central current sheets: Observations with Parker Solar Probe

    , Astronomy & Astrophysics, Vol: 650, Pages: 1-12, ISSN: 0004-6361

    Aims. We report the observation by Parker Solar Probe (PSP) of magnetic structures in the solar wind that present a strong peak intheir magnetic field magnitude with an embedded central current sheet. Similar structures have been observed, either at the Earth’smagnetopause and called interlinked flux tubes, or in the solar wind and called interplanetary field enhancements.Methods. In this work, we first investigate two striking events in detail; one occurred in the regular slow solar wind on November 2,2018 and the other was observed during a heliospheric current sheet crossing on November 13, 2018. They both show the presenceof a central current sheet with a visible ion jet and general characteristics consistent with the occurrence of magnetic reconnection.We then performed a survey of PSP data from encounters 1 to 4 and find 18 additional events presenting an increase in the magneticfield magnitude of over 30% and a central current sheet. We performed a statistical study on the 20 "magnetic increases with centralcurrent sheet" (MICCS), with 13 observed in the regular slow solar wind with a constant polarity (i.e., identical strahl direction), and7 which were specifically observed near a heliospheric current sheet (HCS) crossing.Results. We analyze and discuss the general properties of the structures, including the duration, location, amplitude, and magnetictopology, as well as the characteristics of their central current sheet. We find that the latter has a preferential orientation in the TNplane of the RTN frame. We also find no significant change in the dust impact rate in the vicinity of the MICCS under study, leadingus to conclude that dust probably plays no role in the MICCS formation and evolution. Our findings are overall consistent with adouble flux tube-configuration that would result from initially distinct flux tubes which interact during solar wind propagation.
  • Journal article
    Chen CHK, Chandran BDG, Woodham LD, Jones SI, Perez JC, Bourouaine S, Bowen TA, Klein KG, Moncuquet M, Kasper JC, Bale SDet al., 2021,

    The near-Sun streamer belt solar wind: turbulence and solar wind acceleration

    , Astronomy & Astrophysics, Vol: 650, Pages: 1-6, ISSN: 0004-6361

    The fourth orbit of Parker Solar Probe (PSP) reached heliocentric distances down to 27.9 R⊙, allowing solar wind turbulence and acceleration mechanisms to be studied in situ closer to the Sun than previously possible. The turbulence properties were found to be significantly different in the inbound and outbound portions of PSP’s fourth solar encounter, which was likely due to the proximity to the heliospheric current sheet (HCS) in the outbound period. Near the HCS, in the streamer belt wind, the turbulence was found to have lower amplitudes, higher magnetic compressibility, a steeper magnetic field spectrum (with a spectral index close to –5/3 rather than –3/2), a lower Alfvénicity, and a ‘1∕f’ break at much lower frequencies. These are also features of slow wind at 1 au, suggesting the near-Sun streamer belt wind to be the prototypical slow solar wind. The transition in properties occurs at a predicted angular distance of ≈4° from the HCS, suggesting ≈8° as the full-width of the streamer belt wind at these distances. While the majority of the Alfvénic turbulence energy fluxes measured by PSP are consistent with those required for reflection-driven turbulence models of solar wind acceleration, the fluxes in the streamer belt are significantly lower than the model predictions, suggesting that additional mechanisms are necessary to explain the acceleration of the streamer belt solar wind.
  • Journal article
    Liu M, Issautier K, Meyer-Vernet N, Moncuquet M, Maksimovic M, Halekas JS, Huang J, Griton L, Bale S, Bonnell JW, Case AW, Goetz K, Harvey PR, Kasper JC, MacDowall RJ, Malaspina DM, Pulupa M, Stevens MLet al., 2021,

    Solar wind energy flux observations in the inner heliosphere: first results from Parker Solar Probe

    , ASTRONOMY & ASTROPHYSICS, Vol: 650, ISSN: 0004-6361
  • Journal article
    Zhao L-L, Zank GP, Hu Q, Telloni D, Chen Y, Adhikari L, Nakanotani M, Kasper JC, Huang J, Bale SD, Korreck KE, Case AW, Stevens M, Bonnell JW, de Wit TD, Goetz K, Harvey PR, MacDowall RJ, Malaspina DM, Pulupa M, Larson DE, Livi R, Whittlesey P, Klein KG, Raouafi NEet al., 2021,

    Detection of small magnetic flux ropes from the third and fourth Parker Solar Probe encounters

    , ASTRONOMY & ASTROPHYSICS, Vol: 650, ISSN: 0004-6361
  • Journal article
    Larosa A, Krasnoselskikh V, de Wit TD, Agapitov O, Froment C, Jagarlamudi VK, Velli M, Bale SD, Case AW, Goetz K, Harvey P, Kasper JC, Korreck KE, Larson DE, MacDowall RJ, Malaspina D, Pulupa M, Revillet C, Stevens MLet al., 2021,

    Switchbacks: statistical properties and deviations from Alfvenicity

    , ASTRONOMY & ASTROPHYSICS, Vol: 650, ISSN: 0004-6361
  • Journal article
    Badman ST, Bale SD, Rouillard AP, Bowen TA, Bonnell JW, Goetz K, Harvey PR, MacDowall RJ, Malaspina DM, Pulupa Met al., 2021,

    Measurement of the open magnetic flux in the inner heliosphere down to 0.13 AU

    , ASTRONOMY & ASTROPHYSICS, Vol: 650, ISSN: 0004-6361
  • Journal article
    Bandyopadhyay R, Matthaeus WH, McComas DJ, Joyce CJ, Szalay JR, Christian ER, Giacalone J, Schwadron NA, Mitchell DG, Hill ME, McNutt RL, Desai M, Bale SD, Bonnell JW, de Wit TD, Goetz K, Harvey PR, MacDowall RJ, Malaspina DM, Pulupa M, Kasper JC, Stevens Met al., 2021,

    Energetic particle behavior in near-Sun magnetic field switchbacks from PSP

    , ASTRONOMY & ASTROPHYSICS, Vol: 650, ISSN: 0004-6361
  • Journal article
    Joyce CJ, McComas DJ, Schwadron NA, Christian ER, Wiedenbeck ME, McNutt RL, Cohen CMS, Leske RA, Mewaldt RA, Stone EC, Labrador AW, Davis AJ, Cummings AC, Mitchell DG, Hill ME, Roelof EC, Allen RC, Szalay JR, Rankin JS, Desai M, Giacalone J, Matthaeus WH, Bale SD, Kasper JCet al., 2021,

    Time evolution of stream interaction region energetic particle spectra in the inner heliosphere

    , ASTRONOMY & ASTROPHYSICS, Vol: 650, ISSN: 0004-6361
  • Journal article
    Zhang Z, Desai R, Miyake Y, Usui H, Shebanits Oet al., 2021,

    Particle-in-cell simulations of the Cassini spacecraft’s interaction with Saturn’s ionosphere during the Grand Finale

    , Monthly Notices of the Royal Astronomical Society, Vol: 504, Pages: 964-973, ISSN: 0035-8711

    A surprising and unexpected phenomenon observed during Cassini’s Grand Finale was the spacecraft charging to positive potentials in Saturn’s ionosphere. Here, the ionospheric plasma was depleted of free electrons with negatively charged ions and dust accumulating up to over 95 per cent of the negative charge density. To further understand the spacecraft–plasma interaction, we perform a three-dimensional Particle-In-Cell study of a model Cassini spacecraft immersed in plasma representative of Saturn’s ionosphere. The simulations reveal complex interaction features such as electron wings and a highly structured wake containing spacecraft-scale vortices. The results show how a large negative ion concentration combined with a large negative to positive ion mass ratio is able to drive the spacecraft to the observed positive potentials. Despite the high electron depletions, the electron properties are found as a significant controlling factor for the spacecraft potential together with the magnetic field orientation which induces a potential gradient directed across Cassini’s asymmetric body. This study reveals the global spacecraft interaction experienced by Cassini during the Grand Finale and how this is influenced by the unexpected negative ion and dust populations.
  • Journal article
    Desai RT, Zhang Z, Wu X, Lue Cet al., 2021,

    Photodetachment and Test-particle Simulation Constraints on Negative Ions in Solar System Plasmas

    , The Planetary Science Journal, Vol: 2, Pages: 99-99

    <jats:title>Abstract</jats:title> <jats:p>Negative ions have been detected in abundance in recent years by spacecraft across the solar system. These detections were, however, made by instruments not designed for this purpose and, as such, significant uncertainties remain regarding the prevalence of these unexpected plasma components. In this article, the phenomenon of photodetachment is examined, and experimentally and theoretically derived cross-sections are used to calculate photodetachment rates for a range of atomic and molecular negative ions subjected to the solar photon spectrum. These rates are applied to negative ions outflowing from Europa, Enceladus, Titan, Dione, and Rhea and their trajectories are traced to constrain source production rates and the extent to which negative ions are able to pervade the surrounding space environments. Predictions are also made for further negative ion populations in the outer solar system with Triton used as an illustrative example. This study demonstrates how, at increased heliocentric distances, negative ions can form stable ambient plasma populations and can be exploited by future missions to the outer solar system.</jats:p>
  • Journal article
    Quijia P, Fraternale F, Stawarz J, Vásconez C, Perri S, Marino R, Yordanova E, Sorriso-Valvo Let al., 2021,

    Comparing turbulence in a Kelvin-Helmholtz instability region across the terrestrial magnetopause

    , Monthly Notices of the Royal Astronomical Society, Vol: 503, Pages: 4815-4827, ISSN: 0035-8711

    The properties of turbulence observed within the plasma originating from the magnetosheath and the magnetospheric boundary layer, which have been entrained within vortices driven by the Kelvin–Helmholtz Instability (KHI), are compared. The goal of such a study is to determine similarities and differences between the two different regions. In particular, we study spectra, intermittency and the third-order moment scaling, as well as the distribution of a local energy transfer rate proxy. The analysis is performed using the Magnetospheric Multiscale data from a single satellite that crosses longitudinally the KHI. Two sets of regions, one set containing predominantly magnetosheath plasma and the other containing predominantly magnetospheric plasma, are analysed separately, thus allowing us to explore turbulence properties in two portions of very different plasma samples. Results show that the dynamics in the two regions is different, with the boundary layer plasma presenting a shallower spectra and larger energy transfer rate, indicating an early stage of turbulence. In both regions, the effect of the KHI is evidenced.
  • Journal article
    Quijia P, Fraternale F, Stawarz JE, Vasconez CL, Perri S, Marino R, Yordanova E, Sorriso-Valvo Let al., 2021,

    Comparing turbulence in a Kelvin-Helmholtz instability region across the terrestrial magnetopause (vol 503, pg 4815, 2021)

    , MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 503, Pages: 4828-4828, ISSN: 0035-8711
  • Journal article
    Johlander A, Battarbee M, Vaivads A, Turc L, Pfau-Kempf Y, Ganse U, Grandin M, Dubart M, Khotyaintsev YV, Caprioli D, Haggerty C, Schwartz SJ, Giles BL, Palmroth Met al., 2021,

    Ion Acceleration Efficiency at the Earth's Bow Shock: Observations and Simulation Results

    , ASTROPHYSICAL JOURNAL, Vol: 914, ISSN: 0004-637X
  • Journal article
    Weiss Z, Concepcion-Mairey F, Pickering JC, Smid Pet al., 2021,

    Emission spectroscopic study of an analytical glow discharge with plane and hollow cathodes: Titanium and iron in argon discharge

    , SPECTROCHIMICA ACTA PART B-ATOMIC SPECTROSCOPY, Vol: 180, ISSN: 0584-8547
  • Journal article
    Starkey MJ, Fuselier SA, Desai MI, Schwartz SJ, Russell CT, Wei H, Madanian H, Mukherjee J, Wilson LBet al., 2021,

    MMS Observations of Energized He<SUP>+</SUP> Pickup Ions at Quasiperpendicular Shocks

    , ASTROPHYSICAL JOURNAL, Vol: 913, ISSN: 0004-637X
  • Journal article
    Gonzalez CA, Tenerani A, Matteini L, Hellinger P, Velli Met al., 2021,

    Proton Energization by Phase Steepening of Parallel-propagating Alfvenic Fluctuations

    , ASTROPHYSICAL JOURNAL LETTERS, Vol: 914, ISSN: 2041-8205
  • Journal article
    Schwartz SJ, Ergun RE, Harald K, Wilson LB, Chen L-J, Goodrich KA, Turner DL, Gingell I, Madanian H, Gershman DJ, Strangeway RJet al., 2021,

    Evaluating the de Hoffmann-Teller cross-shock potential at real collisionless shocks
  • Journal article
    Kuhn-Régnier A, Voulgarakis A, Nowack P, Forkel M, Prentice IC, Harrison SPet al., 2020,

    Supplementary material to &quot;Quantifying the Importance of Antecedent Fuel-Related VegetationProperties for Burnt Area using Random Forests&quot;

    , Biogeosciences, ISSN: 1726-4170
  • Journal article
    Telloni D, Sorriso-Valvo L, Woodham LD, Panasenco O, Velli M, Carbone F, Zank GP, Bruno R, Perrone D, Nakanotani M, Shi C, D'Amicis R, De Marco R, Jagarlamudi VK, Steinvall K, Marino R, Adhikari L, Zhao L, Liang H, Tenerani A, Laker R, Horbury TS, Bale SD, Pulupa M, Malaspina DM, MacDowall RJ, Goetz K, de Wit TD, Harvey PR, Kasper JC, Korreck KE, Larson D, Case AW, Stevens ML, Whittlesey P, Livi R, Owen CJ, Livi S, Louarn P, Antonucci E, Romoli M, O'Brien H, Evans V, Angelini Vet al., 2021,

    Evolution of solar wind turbulence from 0.1 to 1 au during the first parker solar probe-solar orbiter radial alignment

    , Letters of the Astrophysical Journal, Vol: 912, Pages: 1-8, ISSN: 2041-8205

    The first radial alignment between Parker Solar Probe and Solar Orbiter spacecraft is used to investigate the evolution of solar wind turbulence in the inner heliosphere. Assuming ballistic propagation, two 1.5 hr intervals are tentatively identified as providing measurements of the same plasma parcels traveling from 0.1 to 1 au. Using magnetic field measurements from both spacecraft, the properties of turbulence in the two intervals are assessed. Magnetic spectral density, flatness, and high-order moment scaling laws are calculated. The Hilbert–Huang transform is additionally used to mitigate short sample and poor stationarity effects. Results show that the plasma evolves from a highly Alfvénic, less-developed turbulence state near the Sun, to fully developed and intermittent turbulence at 1 au. These observations provide strong evidence for the radial evolution of solar wind turbulence.
  • Journal article
    Galand M, Feldman PD, Bockelee-Morvan D, Biver N, Cheng Y-C, Rinaldi G, Rubin M, Altwegg K, Deca J, Beth A, Stephenson P, Heritier KL, Henri P, Parker JW, Carr C, Eriksson AI, Burch Jet al., 2021,

    Far-ultraviolet aurora identified at comet 67P/Churyumov-Gerasimenko (vol 4, pg 1084, 2020)

    , NATURE ASTRONOMY, ISSN: 2397-3366
  • Journal article
    Gibbins G, Haigh JD, 2021,

    Comments on "global and regional entropy production by radiation Estimated from satellite observations"

    , Journal of Climate, Vol: 34, Pages: 3721-3728, ISSN: 0894-8755

    A recent paper by Kato and Rose reports a negative correlation between the annual mean entropy production rate of the climate and the absorption of solar radiation in the CERES SYN1deg dataset, using the simplifying assumption that the system is steady in time. It is shown here, however, that when the nonsteady interannual storage of entropy is accounted for, the dataset instead implies a positive correlation; that is, global entropy production rates increase with solar absorption. Furthermore, this increase is consistent with the response demonstrated by an energy balance model and a radiative–convective model. To motivate this updated analysis, a detailed discussion of the conceptual relationship between entropy production, entropy storage, and entropy flows is provided. The storage-corrected estimate for the mean global rate of entropy production in the CERES dataset from all irreversible transfer processes is 81.9 mW m−2 K−1 and from only nonradiative processes is 55.2 mW m−2 K−1 (observations from March 2000 to February 2018).
  • Journal article
    Cheng IK, Achilleos N, Masters A, Lewis GR, Kane M, Guio Pet al., 2021,

    Electron bulk heating at Saturn's magnetopause

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

    Magnetic reconnection at the magnetopause (MP) energizes ambient plasma via the release of magnetic energy and produces an “open” magnetosphere allowing solar wind particles to directly enter the system. At Saturn, the nature of MP reconnection remains unclear. The current study examines electron bulk heating at MP crossings, in order to probe the relationship between observed and predicted reconnection heating proposed by Phan et al. (2013, https://doi.org/10.1002/grl.50917) under open and closed MP, and how this may pertain to the position of the crossings in the Δβ‐magnetic shear parameter space. The electron heating for 70 MP crossings made by the Cassini spacecraft from April 2005 to July 2007 was found using 1d and 3d moment methods. Minimum variance analysis was used on the magnetic field data to help indicate whether the MP is open or closed. We found better agreement between observed and predicted heating for events suggestive of locally “open” MP. For events suggestive of locally “closed” MP, we observed a cluster of points consistent with no electron heating, but also numerous cases with significant heating. Examining the events in the Δβ‐magnetic shear parameter space, we find 83% of events without evidence of energization were situated in the “reconnection suppressed” regime, whilst between 43% to 68% of events with energization lie in the “reconnection possible” regime depending on the threshold used. The discrepancies could be explained by a combination of spatial and temporal variability which makes it possible to observe heated electrons with different conditions from the putative reconnection site.
  • Journal article
    Lai T-K, Hendricks EA, Yau MK, Menelaou Ket al., 2021,

    Roles of Barotropic Instability across the Moat in Inner Eyewall Decay and Outer Eyewall Intensification: Essential Dynamics

    , JOURNAL OF THE ATMOSPHERIC SCIENCES, Vol: 78, Pages: 1411-1428, ISSN: 0022-4928

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