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  • Journal article
    Greaves JS, Richards AMS, Bains W, Rimmer PB, Sagawa H, Clements DL, Seager S, Petkowski JJ, Sousa-Silva C, Ranjan S, Drabek-Maunder E, Fraser HJ, Cartwright A, Mueller-Wodarg I, Zhan Z, Friberg P, Coulson I, Lee E, Hoge Jet al., 2021,

    Phosphine gas in the cloud deck of Venus (vol 5, pg 655, 2021)

    , Nature Astronomy, Vol: 5, Pages: 726-728, ISSN: 2397-3366
  • Journal article
    Joyce CJ, McComas DJ, Schwadron NA, Vourlidas A, Christian ER, McNutt RL, Cohen CMS, Leske RA, Mewaldt RA, Stone EC, Mitchell DG, Hill ME, Roelof EC, Allen RC, Szalay JR, Rankin JS, Desai M, Giacalone J, Matthaeus WH, Niehof JT, de Wet W, Winslow RM, Bale SD, Kasper JCet al., 2021,

    Energetic particle evolution during coronal mass ejection passage from 0.3 to 1 AU

    , ASTRONOMY & ASTROPHYSICS, Vol: 651, ISSN: 0004-6361
  • Journal article
    Madanian H, Schwartz SJ, Fuselier SA, Burgess D, Turner DL, Chen L-J, Desai MI, Starkey MJet al., 2021,

    Direct Evidence for Magnetic Reflection of Heavy Ions from High Mach Number Collisionless Shocks

    , ASTROPHYSICAL JOURNAL LETTERS, Vol: 915, ISSN: 2041-8205
  • Journal article
    Yao Z, Dunn WR, Woodfield EE, Clark G, Mauk BH, Ebert RW, Grodent D, Bonfond B, Pan D, Rae IJ, Ni B, Guo R, Branduardi-Raymont G, Wibisono AD, Rodriguez P, Kotsiaros S, Ness J-U, Allegrini F, Kurth WS, Gladstone GR, Kraft R, Sulaiman AH, Manners H, Desai RT, Bolton SJet al., 2021,

    Revealing the source of Jupiter's x-ray auroral flares

    , SCIENCE ADVANCES, Vol: 7, ISSN: 2375-2548
    • Cite
    • Citations: 14
  • Journal article
    Duan D, He J, Bowen TA, Woodham LD, Wang T, Chen CHK, Mallet A, Bale SDet al., 2021,

    Anisotropy of solar wind turbulence in the inner heliosphere at kinetic scales: PSP observations

    , Letters of the Astrophysical Journal, Vol: 915, Pages: 1-7, ISSN: 2041-8205

    The anisotropy of solar wind turbulence is a critical issue in understanding the physics of energy transfer between scales and energy conversion between fields and particles in the heliosphere. Using the measurement of Parker Solar Probe (PSP), we present an observation of the anisotropy at kinetic scales in the slow, Alfvénic, solar wind in the inner heliosphere. The magnetic compressibility behaves as expected for kinetic Alfvénic turbulence below the ion scale. A steepened transition range is found between the inertial and kinetic ranges in all directions with respect to the local background magnetic field direction. The anisotropy of k⊥ ≫ k∥ is found evident in both transition and kinetic ranges, with the power anisotropy P⊥/P∥ > 10 in the kinetic range leading over that in the transition range and being stronger than that at 1 au. The spectral index varies from αt∥ = −5.7 ± 1.0 to αt⊥ = −3.7 ± 0.3 in the transition range and αk∥ = −3.12 ± 0.22 to αk⊥ = −2.57 ± 0.09 in the kinetic range. The corresponding wavevector anisotropy has the scaling of ${k}_{\parallel }\sim {k}_{\perp }^{0.71\pm 0.17}$ in the transition range, and changes to ${k}_{\parallel }\sim {k}_{\perp }^{0.38\pm 0.09}$ in the kinetic range, consistent with the kinetic Alfvénic turbulence at sub-ion scales.
  • Journal article
    Wang R, Vasko IY, Mozer FS, Bale SD, Kuzichev IV, Artemyev AV, Steinvall K, Ergun R, Giles B, Khotyaintsev Y, Lindqvist P-A, Russell CT, Strangeway Ret al., 2021,

    Electrostatic Solitary Waves in the Earth's Bow Shock: Nature, Properties, Lifetimes, and Origin

    , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 126, ISSN: 2169-9380
  • Journal article
    Gristey JJ, Su W, Loeb NG, Vonder Haar TH, Tornow F, Schmidt KS, Hakuba MZ, Pilewskie P, Russell JEet al., 2021,

    Shortwave radiance to irradiance conversion for earth radiation budget satellite observations: a review

    , Remote Sensing, Vol: 13, ISSN: 2072-4292

    Observing the Earth radiation budget (ERB) from satellites is crucial for monitoring and understanding Earth’s climate. One of the major challenges for ERB observations, particularly for reflected shortwave radiation, is the conversion of the measured radiance to the more energetically relevant quantity of radiative flux, or irradiance. This conversion depends on the solar-viewing geometry and the scene composition associated with each instantaneous observation. We first outline the theoretical basis for algorithms to convert shortwave radiance to irradiance, most commonly known as empirical angular distribution models (ADMs). We then review the progression from early ERB satellite observations that applied relatively simple ADMs, to current ERB satellite observations that apply highly sophisticated ADMs. A notable development is the dramatic increase in the number of scene types, made possible by both the extended observational record and the enhanced scene information now available from collocated imager information. Compared with their predecessors, current shortwave ADMs result in a more consistent average albedo as a function of viewing zenith angle and lead to more accurate instantaneous and mean regional irradiance estimates. One implication of the increased complexity is that the algorithms may not be directly applicable to observations with insufficient accompanying imager information, or for existing or new satellite instruments where detailed scene information is not available. Recent advances that complement and build on the base of current approaches, including machine learning applications and semi-physical calculations, are highlighted.
  • Journal article
    Farrell WM, Rasca AP, MacDowall RJ, Gruesbeck JR, Bale SD, Kasper JCet al., 2021,

    Switchback Boundary Dissipation and Relative Age

    , ASTROPHYSICAL JOURNAL, Vol: 915, ISSN: 0004-637X
  • Journal article
    Chen L, Ma B, Wu D, Zhao G, Tang J, Bale SDet al., 2021,

    An Interplanetary Type IIIb Radio Burst Observed by Parker Solar Probe and Its Emission Mechanism

    , ASTROPHYSICAL JOURNAL LETTERS, Vol: 915, ISSN: 2041-8205
  • Journal article
    Halekas JS, Bercic L, Whittlesey P, Larson DE, Livi R, Berthomier M, Kasper JC, Case AW, Stevens ML, Bale SD, MacDowall RJ, Pulupa MPet al., 2021,

    The Sunward Electron Deficit: A Telltale Sign of the Sun's Electric Potential

    , ASTROPHYSICAL JOURNAL, Vol: 916, ISSN: 0004-637X
  • Journal article
    Kuhn- Regnier A, Voulgarakis A, Nowack P, Forkel M, Prentice IC, Harrison Set al., 2021,

    The importance of antecedent vegetation and drought conditions as global drivers of burnt areas

    , Biogeosciences, Vol: 18, Pages: 3861-3879, ISSN: 1726-4170

    The seasonal and longer-term dynamics of fuel accumulation affect fire seasonality and the occurrence of extreme wildfires. Failure to account for their influence may help to explain why state-of-the-art fire models do not simulate the length and timing of the fire season or interannual variability in burnt area well. We investigated the impact of accounting for different timescales of fuel production and accumulation on burnt area using a suite of random forest regression models that included the immediate impact of climate, vegetation, and human influences in a given month and tested the impact of various combinations of antecedent conditions in four productivity-related vegetation indices and in antecedent moisture conditions. Analyses were conducted for the period from 2010 to 2015 inclusive. Inclusion of antecedent vegetation conditions representing fuel build-up led to an improvement of the global, climatological out-of-sample R2 from 0.579 to 0.701, but the inclusion of antecedent vegetation conditions on timescales ≥ 1 year had no impact on simulated burnt area. Current moisture levels were the dominant influence on fuel drying. Additionally, antecedent moisture levels were important for fuel build-up. The models also enabled the visualisation of interactions between variables, such as the importance of antecedent productivity coupled with instantaneous drying. The length of the period which needs to be considered varies across biomes; fuel-limited regions are sensitive to antecedent conditions that determine fuel build-up over longer time periods (∼ 4 months), while moisture-limited regions are more sensitive to current conditions that regulate fuel drying.
  • Journal article
    Kuhn-Régnier A, Voulgarakis A, Nowack P, Forkel M, Prentice IC, Harrison SPet al., 2021,

    Quantifying the Importance of antecedent fuel-related vegetationproperties for burnt area using random forests

    , Biogeosciences, Vol: 8, ISSN: 1726-4170

    The seasonal and longer-term dynamics of fuel accumulation affect fire seasonality and the occurrence of extreme wildfires. Failure to account for their influence mayhelp to explain why state-of-the-art fire models do not simulate the length and timing of the fire season or interannual variability in burnt area well. We investigated the impact of accounting for different timescales of fuel production and accumulation on burnt area using a suite of random forest regression models that included the immediateimpact of climate, vegetation, and human influences in agiven month and tested the impact of various combinationsof antecedent conditions in four productivity-related vegetation indices and in antecedent moisture conditions. Analyses were conducted for the period from 2010 to 2015 inclusive. Inclusion of antecedent vegetation conditions representing fuel build-up led to an improvement of the global,climatological out-of-sample R2from 0.579 to 0.701, but theinclusion of antecedent vegetation conditions on timescales≥ 1 year had no impact on simulated burnt area. Currentmoisture levels were the dominant influence on fuel drying. Additionally, antecedent moisture levels were importantfor fuel build-up. The models also enabled the visualisationof interactions between variables, such as the importanceof antecedent productivity coupled with instantaneous drying. The length of the period which needs to be consideredvaries across biomes; fuel-limited regions are sensitive to antecedent conditions that determine fuel build-up over longertime periods (∼ 4 months), while moisture-limited regionsare more sensitive to current conditions that regulate fuel drying.
  • Journal article
    Malaspina DM, Wilson LB, Ergun RE, Bale SD, Bonnell JW, Goodrich K, Goetz K, Harvey PR, MacDowall RJ, Pulupa M, Halekas J, Case A, Kasper JC, Larson D, Stevens M, Whittlesey Pet al., 2021,

    Electron Bernstein waves and narrowband plasma waves near the electron cyclotron frequency in the near-Sun solar wind

    , ASTRONOMY & ASTROPHYSICS, Vol: 650, ISSN: 0004-6361
    • Cite
    • Citations: 13
  • 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
    Stansby D, Bercic L, Matteini L, Owen CJ, French RJ, Baker D, Badman STet al., 2021,

    Sensitivity of solar wind mass flux to coronal temperature

    , 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
    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
    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
    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
    • Cite
    • Citations: 16

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