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  • 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
    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
    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
    Cohen CMS, Christian ER, Cummings AC, Davis AJ, Desai M, de Nolfo GA, Giacalone J, Hill ME, Joyce CJ, Labrador AW, Leske RA, Matthaeus WH, McComas DJ, McNutt RL, Mewaldt RA, Mitchell DG, Mitchell JG, Rankin JS, Roelof EC, Schwadron NA, Stone EC, Szalay JR, Wiedenbeck ME, Vourlidas A, Bale SD, Pulupa M, MacDowall RJet al., 2021,

    Parker Solar Probe observations of He/H abundance variations in SEP events inside 0.5 au

    , ASTRONOMY & ASTROPHYSICS, Vol: 650, ISSN: 0004-6361
  • Journal article
    Vech D, Martinovic MM, Klein KG, Malaspina DM, Bowen TA, Verniero JL, Paulson K, de Wit TD, Kasper JC, Huang J, Stevens ML, Case AW, Korreck K, Mozer FS, Goodrich KA, Bale SD, Whittlesey PL, Livi R, Larson DE, Pulupa M, Bonnell J, Harvey P, Goetz K, MacDowall Ret al., 2021,

    Wave-particle energy transfer directly observed in an ion cyclotron wave

    , ASTRONOMY & ASTROPHYSICS, Vol: 650, ISSN: 0004-6361
  • Journal article
    Allen RC, Ho GC, Jian LK, Vines SK, Bale SD, Case AW, Hill ME, Joyce CJ, Kasper JC, Korreck KE, Malaspina DM, McComas DJ, McNutt R, Mostl C, Odstrcil D, Raouafi N, Schwadron NA, Stevens MLet al., 2021,

    A living catalog of stream interaction regions in the Parker Solar Probe era

    , ASTRONOMY & ASTROPHYSICS, Vol: 650, ISSN: 0004-6361
  • Journal article
    Cattell C, Glesener L, Leiran B, Dombeck J, Goetz K, Oliveros JCM, Badman ST, Pulupa M, Bale SDet al., 2021,

    Periodicities in an active region correlated with Type Ill radio bursts observed by Parker Solar Probe

    , ASTRONOMY & ASTROPHYSICS, Vol: 650, ISSN: 0004-6361
  • 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
    Laker R, Horbury TS, Bale SD, Matteini L, Woolley T, Woodham LD, Badman ST, Pulupa M, Kasper JC, Stevens M, Case AW, Korreck KEet al., 2021,

    Statistical analysis of orientation, shape, and size of solar wind switchbacks

    , Astronomy & Astrophysics, Vol: 650, Pages: 1-7, ISSN: 0004-6361

    One of the main discoveries from the first two orbits of Parker Solar Probe(PSP) was the presence of magnetic switchbacks, whose deflections dominated themagnetic field measurements. Determining their shape and size could provideevidence of their origin, which is still unclear. Previous work with a singlesolar wind stream has indicated that these are long, thin structures althoughthe direction of their major axis could not be determined. We investigate ifthis long, thin nature extends to other solar wind streams, while determiningthe direction along which the switchbacks within a stream were aligned. We tryto understand how the size and orientation of the switchbacks, along with theflow velocity and spacecraft trajectory, combine to produce the observedstructure durations for past and future orbits. We searched for the alignmentdirection that produced a combination of a spacecraft cutting direction andswitchback duration that was most consistent with long, thin structures. Theexpected form of a long, thin structure was fitted to the results of the bestalignment direction, which determined the width and aspect ratio of theswitchbacks for that stream. The switchbacks had a mean width of $50,000 \,\rm{km}$, with an aspect ratio of the order of $10$. We find that switchbacksare not aligned along the background flow direction, but instead aligned alongthe local Parker spiral, perhaps suggesting that they propagate along themagnetic field. Since the observed switchback duration depends on how thespacecraft cuts through the structure, the duration alone cannot be used todetermine the size or influence of an individual event. For future PSP orbits,a larger spacecraft transverse component combined with more radially alignedswitchbacks will lead to long duration switchbacks becoming less common.
  • Journal article
    Woodham L, Horbury T, Matteini L, Woolley T, Laker R, Bale S, Nicolaou G, Stawarz J, Stansby D, Hietala H, Larson D, Livi R, Verniero J, McManus M, Kasper J, Korreck K, Raouafi N, Moncuquet M, Pulupa Met al., 2021,

    Enhanced proton parallel temperature inside patches of switchbacks in the inner heliosphere

    , Astronomy and Astrophysics: a European journal, Vol: 650, Pages: 1-7, ISSN: 0004-6361

    Context. Switchbacks are discrete angular deflections in the solar wind magnetic field that have been observed throughout the helio-sphere. Recent observations by Parker Solar Probe(PSP) have revealed the presence of patches of switchbacks on the scale of hours to days, separated by ‘quieter’ radial fields. Aims. We aim to further diagnose the origin of these patches using measurements of proton temperature anisotropy that can illuminate possible links to formation processes in the solar corona. Methods. We fit 3D bi-Maxwellian functions to the core of proton velocity distributions measured by the SPAN-Ai instrument onboard PSP to obtain the proton parallel, Tp,‖, and perpendicular, Tp,⊥, temperature. Results. We show that the presence of patches is highlighted by a transverse deflection in the flow and magnetic field away from the radial direction. These deflections are correlated with enhancements in Tp,‖, while Tp,⊥remains relatively constant. Patches sometimes exhibit small proton and electron density enhancements. Conclusions. We interpret that patches are not simply a group of switchbacks, but rather switchbacks are embedded within a larger-scale structure identified by enhanced Tp,‖that is distinct from the surrounding solar wind. We suggest that these observations are consistent with formation by reconnection-associated mechanisms in the corona.
  • Journal article
    Drake JF, Agapitov O, Swisdak M, Badman ST, Bale SD, Horbury TS, Kasper JC, MacDowall RJ, Mozer FS, Phan TD, Pulupa M, Szabo A, Velli Met al., 2021,

    Are switchbacks signatures of magnetic flux ropes generated by interchange reconnection in the corona?

    , Astronomy and Astrophysics: a European journal, Vol: 650, Pages: 1-8, ISSN: 0004-6361

    The structure of magnetic flux ropes injected into the solar wind duringreconnection in the coronal atmosphere is explored with particle-in-cellsimulations and compared with {\it in situ} measurements of magnetic"switchbacks" from the Parker Solar Probe. We suggest that multi-x-linereconnection between open and closed flux in the corona will inject flux ropesinto the solar wind and that these flux ropes can convect outward over longdistances before disintegrating. Simulations that explore the magneticstructure of flux ropes in the solar wind reproduce key features of the"switchback" observations: a rapid rotation of the radial magnetic field intothe transverse direction (a consequence of reconnection with a strong guidefield); and the potential to reverse the radial field component. The potentialimplication of the injection of large numbers of flux ropes in the coronalatmosphere for understanding the generation of the solar wind is discussed.
  • Journal article
    Halekas JS, Whittlesey PL, Larson DE, McGinnis D, Bale SD, Berthomier M, Case AW, Chandran BDG, Kasper JC, Klein KG, Korreck KE, Livi R, MacDowall RJ, Maksimovic M, Malaspina DM, Matteini L, Pulupa MP, Stevens MLet al., 2021,

    Electron heat flux in the near-Sun environment

    , ASTRONOMY & ASTROPHYSICS, Vol: 650, ISSN: 0004-6361
  • Journal article
    Shi C, Velli M, Panasenco O, Tenerani A, Reville V, Bale SD, Kasper J, Korreck K, Bonnell JW, de Wit TD, Malaspina DM, Goetz K, Harvey PR, MacDowall RJ, Pulupa M, Case AW, Larson D, Verniero JL, Livi R, Stevens M, Whittlesey P, Maksimovic M, Moncuquet Met al., 2021,

    Alfvenic versus non-Alfvenic turbulence in the inner heliosphere as observed by Parker Solar Probe

    , ASTRONOMY & ASTROPHYSICS, Vol: 650, ISSN: 0004-6361
  • Journal article
    Jagarlamudi VK, de Wit TD, Froment C, Krasnoselskikh V, Larosa A, Bercic L, Agapitov O, Halekas JS, Kretzschmar M, Malaspina D, Moncuquet M, Bale SD, Case AW, Kasper JC, Korreck KE, Larson DE, Pulupa M, Stevens ML, Whittlesey Pet al., 2021,

    Whistler wave occurrence and the interaction with strahl electrons during the first encounter of Parker Solar Probe

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

    Direct evidence for magnetic reconnection at the boundaries of magnetic switchbacks with Parker Solar Probe

    , ASTRONOMY & ASTROPHYSICS, Vol: 650, ISSN: 0004-6361
  • 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
    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
    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
    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
    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
    Trotta D, Valentini F, Burgess D, Servidio Set al., 2021,

    Phase space transport in the interaction between shocks and plasma turbulence

    , PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 118, ISSN: 0027-8424

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