# PSP Bibliography

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## Found 137 entries in the Bibliography.

### Showing entries from 1 through 50

 2022 Parker Solar Probe Observations of Near-f $_Ce$ Harmonic Emissions in the Near-Sun Solar Wind and Their Dependence on the Magnetic Field Direction Wave emissions at frequencies near electron gyrofrequency harmonics are observed at small heliocentric distances below about 40 R $_\ensuremath\odot$ and are known to occur in regions with quiescent magnetic fields. We show the close connection of these waves to the large-scale properties of the magnetic field. Near electron gyrofrequency harmonic emissions occur only when the ambient magnetic field points to a narrow range of directions bounded by polar and azimuthal angular ranges in the RTN coordinate system of correspond ... Tigik, Sabrina; Vaivads, Andris; Malaspina, David; Bale, Stuart; Published by: \apj      Published on: sep YEAR: 2022     DOI: 10.3847/1538-4357/ac8473 The incompressible energy cascade rate in anisotropic solar wind turbulence Context. The presence of a magnetic guide field induces several types of anisotropy in solar wind turbulence. The energy cascade rate between scales in the inertial range depends strongly on the direction of this magnetic guide field, splitting the energy cascade according to the parallel and perpendicular directions with respect to magnetic guide field. \ Aims: Using more than two years of Parker Solar Probe (PSP) observations, the isotropy and anisotropy energy cascade rates are investigated. The variance and normalized fl ... es, Andr\; Sahraoui, F.; Huang, S.; Hadid, L.~Z.; Galtier, S.; Published by: \aap      Published on: may YEAR: 2022     DOI: 10.1051/0004-6361/202142994 Intermittency in the Expanding Solar Wind: Observations from Parker Solar Probe (0.16 au), Helios 1 (0.3-1 au), and Voyager 1 (1-10 au) We examine statistics of magnetic-field vector components to explore how intermittency evolves from near-Sun plasma to radial distances as large as 10 au. Statistics entering the analysis include autocorrelation, magnetic structure functions of the order of n (SF$_ n$), and scale-dependent kurtosis (SDK), each grouped in ranges of heliocentric distance. The Goddard Space Flight Center Space Physics Data Facility provides magnetic-field measurements for resolutions of 6.8 ms for Parker Solar Probe, 6 s for Helios, and 1.92 s ... Cuesta, Manuel; Parashar, Tulasi; Chhiber, Rohit; Matthaeus, William; Published by: \apjs      Published on: mar YEAR: 2022     DOI: 10.3847/1538-4365/ac45fa Relativistic Particle Transport and Acceleration in Structured Plasma Turbulence We discuss the phenomenon of energization of relativistic charged particles in three-dimensional incompressible MHD turbulence and the diffusive properties of the motion of the same particles. We show that the random electric field induced by turbulent plasma motion leads test particles moving in a simulated box to be accelerated in a stochastic way, a second-order Fermi process. A small fraction of these particles happen to be trapped in large- scale structures, most likely formed due to the interaction of islands in the tu ... Pezzi, Oreste; Blasi, Pasquale; Matthaeus, William; Published by: \apj      Published on: mar YEAR: 2022     DOI: 10.3847/1538-4357/ac5332 Core Electron Heating by Triggered Ion Acoustic Waves in the Solar Wind Perihelion passes on Parker Solar Probe orbits 6-9 have been studied to show that solar wind core electrons emerged from 15 solar radii with a temperature of 55 \ensuremath\pm 5 eV, independent of the solar wind speed, which varied from 300 to 800 km s$^-1$. After leaving 15 solar radii and in the absence of triggered ion acoustic waves at greater distances, the core electron temperature varied with radial distance, R, in solar radii, as 1900R $^-4/3$ eV because of cooling produced by the adiabatic expansion. The coefficient ... Mozer, F.~S.; Bale, S.~D.; Cattell, C.~A.; Halekas, J.; Vasko, I.~Y.; Verniero, J.~L.; Kellogg, P.~J.; Published by: \apjl      Published on: mar YEAR: 2022     DOI: 10.3847/2041-8213/ac5520 Statistical Analysis of Intermittency and its Association with Proton Heating in the Near-Sun Environment We use data from the first six encounters of the Parker Solar Probe and employ the partial variance of increments (PVI) method to study the statistical properties of coherent structures in the inner heliosphere with the aim of exploring physical connections between magnetic field intermittency and observable consequences such as plasma heating and turbulence dissipation. Our results support proton heating localized in the vicinity of, and strongly correlated with, magnetic structures characterized by PVI \ensuremath\geq 1. W ... Sioulas, Nikos; Velli, Marco; Chhiber, Rohit; Vlahos, Loukas; Matthaeus, William; Bandyopadhyay, Riddhi; Cuesta, Manuel; Shi, Chen; Bowen, Trevor; Qudsi, Ramiz; Stevens, Michael; Bale, Stuart; Published by: \apj      Published on: mar YEAR: 2022     DOI: 10.3847/1538-4357/ac4fc1 Flux rope and dynamics of the heliospheric current sheet. Study of the Parker Solar Probe and Solar Orbiter conjunction of June 2020 Context. Solar Orbiter and Parker Solar Probe jointly observed the solar wind for the first time in June 2020, capturing data from very different solar wind streams: calm, Alfv\ enic wind and also highly dynamic large-scale structures. Context. Our aim is to understand the origin and characteristics of the highly dynamic solar wind observed by the two probes, particularly in the vicinity of the heliospheric current sheet (HCS). \ Methods: We analyzed the plasma data obtained by Parker Solar Probe and Solar Orbiter in situ du ... Réville, V.; Fargette, N.; Rouillard, A.~P.; Lavraud, B.; Velli, M.; Strugarek, A.; Parenti, S.; Brun, A.~S.; Shi, C.; Kouloumvakos, A.; Poirier, N.; Pinto, R.~F.; Louarn, P.; Fedorov, A.; Owen, C.~J.; enot, V.; Horbury, T.~S.; Laker, R.; Brien, H.; Angelini, V.; Fauchon-Jones, E.; Kasper, J.~C.; Published by: \aap      Published on: mar YEAR: 2022     DOI: 10.1051/0004-6361/202142381 In Situ Measurement of the Energy Fraction in Suprathermal and Energetic Particles at ACE, Wind, and PSP Interplanetary Shocks The acceleration of charged particles by interplanetary shocks (IPs) can drain a nonnegligible fraction of the plasma pressure. In this study, we have selected 17 IPs observed in situ at 1 au by the Advanced Composition Explorer and the Wind spacecraft, and 1 shock at 0.8 au observed by Parker Solar Probe. We have calculated the time-dependent partial pressure of suprathermal and energetic particles (smaller and greater than 50 keV for protons and 30 keV for electrons, respectively) in both the upstream and downstream region ... David, Liam; Fraschetti, Federico; Giacalone, Joe; Wimmer-Schweingruber, Robert; Berger, Lars; Lario, David; Published by: \apj      Published on: mar YEAR: 2022     DOI: 10.3847/1538-4357/ac54af Energy Transfer, Discontinuities, and Heating in the Inner Heliosphere Measured with a Weak and Local Formulation of the Politano-Pouquet Law The solar wind is a highly turbulent plasma for which the mean rate of energy transfer ɛ has been measured for a long time using the Politano-Pouquet (PP98) exact law. However, this law assumes statistical homogeneity that can be violated by the presence of discontinuities. Here, we introduce a new method based on the inertial dissipation $D _I^{\sigma }$ whose analytical form is derived from incompressible magnetohydrodynamics; it can be considered as a weak and local (in space) formulation of the PP98 law whose expressio ... David, V.; Galtier, S.; Sahraoui, F.; Hadid, L.~Z.; Published by: \apj      Published on: mar YEAR: 2022     DOI: 10.3847/1538-4357/ac524b Energetic Particle Perpendicular Diffusion: Simulations and Theory in Noisy Reduced Magnetohydrodynamic Turbulence The transport of energetic charged particles (e.g., cosmic rays) in turbulent magnetic fields is usually characterized in terms of the diffusion parallel and perpendicular to a large-scale (or mean) magnetic field. The nonlinear guiding center theory has been a prominent perpendicular diffusion theory. A recent version of this theory, based on the random ballistic spreading of magnetic field lines and a backtracking correction (RBD/BC), has shown good agreement with test particle simulations for a two-component magnetic turb ... Snodin, A.~P.; Jitsuk, T.; Ruffolo, D.; Matthaeus, W.~H.; Published by: \apj      Published on: jun YEAR: 2022     DOI: 10.3847/1538-4357/ac6e6d Radial Evolution of Thermal and Suprathermal Electron Populations in the Slow Solar Wind from 0.13 to 0.5 au: Parker Solar Probe Observations We develop and apply a bespoke fitting routine to a large volume of solar wind electron distribution data measured by Parker Solar Probe over its first five orbits, covering radial distances from 0.13 to 0.5 au. We characterize the radial evolution of the electron core, halo, and strahl populations in the slow solar wind during these orbits. The fractional densities of these three electron populations provide evidence for the growth of the combined suprathermal halo and strahl populations from 0.13 to 0.17 au. Moreover, the ... Abraham, Joel; Owen, Christopher; Verscharen, Daniel; Bakrania, Mayur; Stansby, David; Wicks, Robert; Nicolaou, Georgios; Whittlesey, Phyllis; Rueda, Jeffersson; Jeong, Seong-Yeop; Ber\vci\vc, Laura; Published by: \apj      Published on: jun YEAR: 2022     DOI: 10.3847/1538-4357/ac6605 Isotropization and Evolution of Energy-containing Eddies in Solar Wind Turbulence: Parker Solar Probe, Helios 1, ACE, WIND, and Voyager 1 We examine the radial evolution of correlation lengths perpendicular ( $\lambda _C^\perp$ ) and parallel ( $\lambda _C^\parallel$ ) to the magnetic-field direction, computed from solar wind magnetic-field data measured by Parker Solar Probe (PSP) during its first eight orbits, Helios 1, Advanced Composition Explorer (ACE), WIND, and Voyager 1 spacecraft. Correlation lengths are grouped by an interval s alignment angle; the angle between the magnetic-field and solar wind velocity vectors (\ensuremath\Theta$_BV$). Parallel a ... Cuesta, Manuel; Chhiber, Rohit; Roy, Sohom; Goodwill, Joshua; Pecora, Francesco; Jarosik, Jake; Matthaeus, William; Parashar, Tulasi; Bandyopadhyay, Riddhi; Published by: \apjl      Published on: jun YEAR: 2022     DOI: 10.3847/2041-8213/ac73fd Growth of Outward Propagating Fast-magnetosonic/Whistler Waves in the Inner Heliosphere Observed by Parker Solar Probe The solar wind in the inner heliosphere has been observed by Parker Solar Probe (PSP) to exhibit abundant wave activities. The cyclotron wave modes responding to ions or electrons are among the most crucial wave components. However, their origin and evolution in the inner heliosphere close to the Sun remains a mystery. Specifically, it remains unknown whether it is an emitted signal from the solar atmosphere or an eigenmode growing locally in the heliosphere due to plasma instability. To address and resolve this controversy, ... He, Jiansen; Wang, Ying; Zhu, Xingyu; Duan, Die; Verscharen, Daniel; Zhao, Guoqing; Published by: \apj      Published on: jul YEAR: 2022     DOI: 10.3847/1538-4357/ac6c8e The Dynamic Evolution of Solar Wind Streams Following Interchange Reconnection Interchange reconnection is thought to play an important role in determining the dynamics and material composition of the slow solar wind that originates from near coronal-hole boundaries. To explore the implications of this process we simulate the dynamic evolution of a solar wind stream along a newly-opened magnetic flux tube. The initial condition is composed of a piecewise continuous dynamic equilibrium in which the regions above and below the reconnection site are extracted from steady-state solutions along open and clo ... Scott, Roger; Bradshaw, Stephen; Linton, Mark; Published by: \apj      Published on: jul YEAR: 2022     DOI: 10.3847/1538-4357/ac7144 Structure and fluctuations of a slow ICME sheath observed at 0.5 au by the Parker Solar Probe Context. Sheath regions ahead of interplanetary coronal mass ejections (ICMEs) are compressed and turbulent global heliospheric structures. Their global and fine-scale structure are outstanding research problems, and only a few studies have been conducted on this topic closer to the Sun than 1 au. Comprehensive knowledge of the sheath structure and embedded fluctuations and of their evolution in interplanetary space is important for understanding their geoeffectiveness, their role in accelerating charged particles to high en ... Kilpua, E.~K.~J.; Good, S.~W.; Ala-Lahti, M.; Osmane, A.; Pal, S.; Soljento, J.~E.; Zhao, L.~L.; Bale, S.; Published by: \aap      Published on: jul YEAR: 2022     DOI: 10.1051/0004-6361/202142191 On the properties of Alfv\ enic switchbacks in the expanding solar wind: Three-dimensional numerical simulations Switchbacks-abrupt reversals of the magnetic field within the solar wind-have been ubiquitously observed by Parker Solar Probe (PSP). Their origin, whether from processes near the solar surface or within the solar wind itself, remains under debate and likely has key implications for solar wind heating and acceleration. Here, using three-dimensional expanding box simulations, we examine the properties of switchbacks arising from the evolution of outwards-propagating Alfv\ en waves in the expanding solar wind in detail. Our go ... Johnston, Zade; Squire, Jonathan; Mallet, Alfred; Meyrand, Romain; Published by: Physics of Plasmas      Published on: jul YEAR: 2022     DOI: 10.1063/5.0097983 Variable Ion Compositions of Solar Energetic Particle Events in the Inner Heliosphere: A Field Line Braiding Model with Compound Injections We propose a model for interpreting highly variable ion composition ratios in solar energetic particle (SEP) events recently observed by the Parker Solar Probe (PSP) at 0.3-0.45 au. We use numerical simulations to calculate SEP propagation in a turbulent interplanetary magnetic field with a Kolmogorov power spectrum from large scales down to the gyration scale of energetic particles. We show that when the source regions of different species are offset by a distance comparable to the size of the source regions, the observed e ... Guo, Fan; Zhao, Lulu; Cohen, Christina; Giacalone, Joe; Leske, R.~A.; Wiedenbeck, M.~E.; Kahler, S.~W.; Li, Xiaocan; Zhang, Qile; Ho, George; Desai, Mihir; Published by: \apj      Published on: jan YEAR: 2022     DOI: 10.3847/1538-4357/ac3233 Parker Solar Probe Evidence for the Absence of Whistlers Close to the Sun to Scatter Strahl and to Regulate Heat Flux Using the Parker Solar Probe FIELDS bandpass-filter data and SWEAP electron data from Encounters 1 through 9, we show statistical properties of narrowband whistlers from \raisebox-0.5ex\textasciitilde16 R $_s$ to \raisebox-0.5ex\textasciitilde130 R $_s$, and compare wave occurrence to electron properties including beta, temperature anisotropy, and heat flux. Whistlers are very rarely observed inside \raisebox-0.5ex\textasciitilde28 R $_s$ (\raisebox-0.5ex\textasciitilde0.13 au). Outside 28 R $_s$, they occur within a narrow ... Cattell, C.; Breneman, A.; Dombeck, J.; Hanson, E.; Johnson, M.; Halekas, J.; Bale, S.~D.; de Wit, Dudok; Goetz, K.; Goodrich, K.; Malaspina, D.; Pulupa, M.; Case, T.; Kasper, J.~C.; Larson, D.; Stevens, M.; Whittlesey, P.; Published by: \apjl      Published on: jan YEAR: 2022     DOI: 10.3847/2041-8213/ac4015 Strong Perpendicular Velocity-space Diffusion in Proton Beams Observed by Parker Solar Probe The SWEAP instrument suite on Parker Solar Probe (PSP) has detected numerous proton beams associated with coherent, circularly polarized, ion-scale waves observed by PSP s FIELDS instrument suite. Measurements during PSP Encounters 4-8 revealed pronounced complex shapes in the proton velocity distribution functions (VDFs), in which the tip of the beam undergoes strong perpendicular diffusion, resulting in VDF level contours that resemble a hammerhead. We refer to these proton beams, with their attendant hammerhead fe ... Verniero, J.~L.; Chandran, B.~D.~G.; Larson, D.~E.; Paulson, K.; Alterman, B.~L.; Badman, S.; Bale, S.~D.; Bonnell, J.~W.; Bowen, T.~A.; de Wit, Dudok; Kasper, J.~C.; Klein, K.~G.; Lichko, E.; Livi, R.; McManus, M.~D.; Rahmati, A.; Verscharen, D.; Walters, J.; Whittlesey, P.~L.; Published by: \apj      Published on: jan YEAR: 2022     DOI: 10.3847/1538-4357/ac36d5 Small-scale Magnetic Flux Ropes and Their Properties Based on In Situ Measurements from the Parker Solar Probe We report small-scale magnetic flux ropes via the in situ measurements from the Parker Solar Probe during the first six encounters, and present additional analyses to supplement our prior work in Chen et al. These flux ropes are detected by the Grad-Shafranov-based algorithm, with their durations and scale sizes ranging from 10 s to \ensuremath\lesssim1 hr and from a few hundred kilometers to 10$^-3$ au, respectively. They include both static structures and those with significant field-aligned plasma flows. Most structures t ... Chen, Yu; Hu, Qiang; Published by: \apj      Published on: jan YEAR: 2022     DOI: 10.3847/1538-4357/ac3487 Slow Shock Formation Upstream of Reconnecting Current Sheets The formation, development, and impact of slow shocks in the upstream regions of reconnecting current layers are explored. Slow shocks have been documented in the upstream regions of magnetohydrodynamic (MHD) simulations of magnetic reconnection as well as in similar simulations with the kglobal kinetic macroscale simulation model. They are therefore a candidate mechanism for preheating the plasma that is injected into the current layers that facilitate magnetic energy release in solar flares. Of particular interest is their ... Arnold, H.; Drake, J.~F.; Swisdak, M.; Guo, F.; Dahlin, J.~T.; Zhang, Q.; Published by: \apj      Published on: feb YEAR: 2022     DOI: 10.3847/1538-4357/ac423b The Stability of the Electron Strahl against the Oblique Fast-magnetosonic/Whistler Instability in the Inner Heliosphere We analyze the micro-kinetic stability of the electron strahl in the solar wind depending on heliocentric distance. The oblique fast- magnetosonic/whistler (FM/W) instability has emerged in the literature as a key candidate mechanism for the effective scattering of the electron strahl into the electron halo population. Using data from the Parker Solar Probe (PSP) and Helios, we compare the measured strahl properties with the analytical thresholds for the oblique FM/W instability in the low- and high-\ensuremath\beta $_\ensur ... Jeong, Seong-Yeop; Abraham, Joel; Verscharen, Daniel; Ber\vci\vc, Laura; Stansby, David; Nicolaou, Georgios; Owen, Christopher; Wicks, Robert; Fazakerley, Andrew; Rueda, Jeffersson; Bakrania, Mayur; Published by: \apjl Published on: feb YEAR: 2022 DOI: 10.3847/2041-8213/ac4dff Flux Rope Merging and the Structure of Switchbacks in the Solar Wind A major discovery of Parker Solar Probe (PSP) was the presence of large numbers of localized increases in the radial solar wind speed and associated sharp deflections of the magnetic field- switchbacks (SBs). A possible generation mechanism of SBs is through magnetic reconnection between open and closed magnetic flux near the solar surface, termed interchange reconnection, that leads to the ejection of flux ropes (FRs) into the solar wind. Observations also suggest that SBs undergo merging, consistent with an FR picture of t ... Agapitov, O.~V.; Drake, J.~F.; Swisdak, M.; Bale, S.~D.; Horbury, T.~S.; Kasper, J.~C.; MacDowall, R.~J.; Mozer, F.~S.; Phan, T.~D.; Pulupa, M.; Raouafi, N.~E.; Velli, M.; Published by: \apj Published on: feb YEAR: 2022 DOI: 10.3847/1538-4357/ac4016 Sub-Alfv\ enic Solar Wind Observed by the Parker Solar Probe: Characterization of Turbulence, Anisotropy, Intermittency, and Switchback In the lower solar coronal regions where the magnetic field is dominant, the Alfv\ en speed is much higher than the wind speed. In contrast, the near-Earth solar wind is strongly super- Alfv\ enic, i.e., the wind speed greatly exceeds the Alfv\ en speed. The transition between these regimes is classically described as the Alfv\ en point but may in fact occur in a distributed Alfv\ en critical region. NASA s Parker Solar Probe (PSP) mission has entered this region, as it follows a series of orbits that gradually approach ... Bandyopadhyay, R.; Matthaeus, W.~H.; McComas, D.~J.; Chhiber, R.; Usmanov, A.~V.; Huang, J.; Livi, R.; Larson, D.~E.; Kasper, J.~C.; Case, A.~W.; Stevens, M.; Whittlesey, P.; Romeo, O.~M.; Bale, S.~D.; Bonnell, J.~W.; de Wit, Dudok; Goetz, K.; Harvey, P.~R.; MacDowall, R.~J.; Malaspina, D.~M.; Pulupa, M.; Published by: \apjl Published on: feb YEAR: 2022 DOI: 10.3847/2041-8213/ac4a5c Magnetic Field Intermittency in the Solar Wind: Parker Solar Probe and SolO Observations Ranging from the Alfv\ en Region up to 1 AU Parker Solar Probe (PSP) and SolO data are utilized to investigate magnetic field intermittency in the solar wind (SW). Small-scale intermittency (20-100 d$_ i $) is observed to radially strengthen when methods relying on higher-order moments are considered (SF$_ q ; SDK), but no clear trend is observed at larger scales. However, lower-order moment-based methods (e.g., partial variance of increments; PVI) are deemed more appropriate for examining the evolution of the bulk of coherent structures (CSs), PVI \ensuremath\geq 3 ... Sioulas, Nikos; Huang, Zesen; Velli, Marco; Chhiber, Rohit; Cuesta, Manuel; Shi, Chen; Matthaeus, William; Bandyopadhyay, Riddhi; Vlahos, Loukas; Bowen, Trevor; Qudsi, Ramiz; Bale, Stuart; Owen, Christopher; Louarn, P.; Fedorov, A.; c, Milan; Stevens, Michael; Case, Anthony; Kasper, Justin; Larson, Davin; Pulupa, Marc; Livi, Roberto; Published by: \apj Published on: aug YEAR: 2022 DOI: 10.3847/1538-4357/ac7aa2 A magnetic flux rope configuration derived by optimization of two-spacecraft In-situ measurements Increasingly one interplanetary coronal mass ejection (ICME) structure can propagate across more than one spacecraft in the solar wind. This usually happens when two or more spacecraft are nearly radially aligned with a relatively small longitudinal separation angle from one another. This provides multi-point measurements of the same structure and enables better characterization and validation of modeling results of the structures embedded in these ICMEs. We report such an event during October 13-14, 2019 when the Solar TErr ... Hu, Qiang; He, Wen; Chen, Yu; Published by: Frontiers in Physics Published on: aug YEAR: 2022 DOI: 10.3389/fphy.2022.960315 Preferential Heating of Protons over Electrons from Coherent Structures during the First Perihelion of the Parker Solar Probe The solar wind undergoes significant heating as it propagates away from the Sun; the exact mechanisms responsible for this heating remain unclear. Using data from the first perihelion of the Parker Solar Probe mission, we examine the properties of proton and electron heating occurring within magnetic coherent structures identified by means of the Partial Variance of Increments (PVI) method. Statistically, regions of space with strong gradients in the magnetic field, PVI \ensuremath\geq 1, are associated with strongly enhance ... Sioulas, Nikos; Shi, Chen; Huang, Zesen; Velli, Marco; Published by: \apjl Published on: aug YEAR: 2022 DOI: 10.3847/2041-8213/ac85de Magnetic Switchback Occurrence Rates in the Inner Heliosphere: Parker Solar Probe and 1 au The subject of switchbacks, defined either as large angular deflections or polarity reversals of the magnetic field, has generated substantial interest in the space physics community since the launch of the Parker Solar Probe (PSP) in 2018. Previous studies have characterized switchbacks in several different ways and have been restricted to data available from the first few orbits. Here, we analyze the frequency of occurrence of switchbacks per unit distance for the first full eight orbits of PSP. In this work, events that r ... Pecora, Francesco; Matthaeus, William; Primavera, Leonardo; Greco, Antonella; Chhiber, Rohit; Bandyopadhyay, Riddhi; Servidio, Sergio; Published by: \apjl Published on: apr YEAR: 2022 DOI: 10.3847/2041-8213/ac62d4 Markovian Features of the Solar Wind at Subproton Scales The interplanetary magnetic field carried out from the Sun by the solar wind displays fluctuations over a wide range of scales. While at large scales, say at frequencies lower than 0.1-1 Hz, fluctuations display the universal character of fully developed turbulence with a well-defined Kolmogorov-like inertial range, the physical and dynamical properties of the small-scale regime as well as their connection with the large-scale ones are still a debated topic. In this work we investigate the near-Sun magnetic field fluctuation ... Benella, Simone; Stumpo, Mirko; Consolini, Giuseppe; Alberti, Tommaso; Carbone, Vincenzo; Laurenza, Monica; Published by: \apjl Published on: apr YEAR: 2022 DOI: 10.3847/2041-8213/ac6107 On the Conservation of Turbulence Energy in Turbulence Transport Models Zank et al. developed models describing the transport of low-frequency incompressible and nearly incompressible turbulence in inhomogeneous flows. The formalism was based on expressing the fluctuating variables in terms of the Elsässar variables and then taking moments subject to various closure hypotheses. The turbulence transport models are different according to whether the plasma beta regime is large, of order unity, or small. Here, we show explicitly that the three sets of turbulence transport models admit a conser ... Wang, B.; Zank, G.~P.; Adhikari, L.; Zhao, L.; Published by: \apj Published on: apr YEAR: 2022 DOI: 10.3847/1538-4357/ac596e Anisotropy of Magnetic Field Spectra at Kinetic Scales of Solar Wind Turbulence as Revealed by the Parker Solar Probe in the Inner Heliosphere Using the Parker Solar Probe data taken in the inner heliosphere, we investigate the power and spatial anisotropy of magnetic field spectra at kinetic scales (i.e., around sub-ion scales) in solar wind turbulence in the inner heliosphere. We find that strong anisotropy of the magnetic spectra occurs at kinetic scales with the strongest power in the perpendicular direction with respect to the local magnetic field (forming an angle \ensuremath\theta_B$with the mean flow velocity). The spectral index of the magnetic spectra ... Huang, S.~Y.; Xu, S.~B.; Zhang, J.; Sahraoui, F.; es, Andr\; He, J.~S.; Yuan, Z.~G.; Deng, X.~H.; Jiang, K.; Wei, Y.~Y.; Xiong, Q.~Y.; Wang, Z.; Yu, L.; Lin, R.~T.; Published by: \apjl Published on: apr YEAR: 2022 DOI: 10.3847/2041-8213/ac5f02 Kinetic-scale Current Sheets in Near-Sun Solar Wind: Properties, Scale-dependent Features and Reconnection Onset We present statistical analysis of 11,200 proton kinetic-scale current sheets (CS) observed by the Parker Solar Probe during 10 days around the first perihelion. The CS thickness {\ensuremath{\lambda}} is in the range from a few to 200 km with the typical value around 30 km, while current densities are in the range from 0.1 to 10 {\ensuremath{\mu}}A m$^{-2}$with the typical value around 0.7 {\ensuremath{\mu}}A m$^{-2}$. These CSs are resolved thanks to magnetic field measurements at 73-290 samples s$^{-1}$resolution. In te ... Lotekar, A.~B.; Vasko, I.~Y.; Phan, T.; Bale, S.~D.; Bowen, T.~A.; Halekas, J.; Artemyev, A.~V.; Khotyaintsev, Yu.; Mozer, F.~S.; Published by: \apj Published on: apr YEAR: 2022 DOI: 10.3847/1538-4357/ac5bd9 2021 Parker solar probe observations of helical structures as boundaries for energetic particles Energetic particle transport in the interplanetary medium is known to be affected by magnetic structures. It has been demonstrated for solar energetic particles in near-Earth orbit studies, and also for the more energetic cosmic rays. In this paper, we show observational evidence that intensity variations of solar energetic particles can be correlated with the occurrence of helical magnetic flux tubes and their boundaries. The analysis is carried out using data from Parker Solar Probe orbit 5, in the period 2020 May 24 to Ju ... Pecora, F.; Servidio, S.; Greco, A.; Matthaeus, W.~H.; McComas, D.~J.; Giacalone, J.; Joyce, C.~J.; Getachew, T.; Cohen, C.~M.~S.; Leske, R.~A.; Wiedenbeck, M.~E.; McNutt, R.~L.; Hill, M.~E.; Mitchell, D.~G.; Christian, E.~R.; Roelof, E.~C.; Schwadron, N.~A.; Bale, S.~D.; Published by: \mnras Published on: sep YEAR: 2021 DOI: 10.1093/mnras/stab2659 Triggered Ion-acoustic Waves in the Solar Wind For more than 12 hr beginning on 2021 January 18, continuous narrowband electrostatic emissions were observed on the Parker Solar Probe near 20 solar radii. The observed <1000 Hz frequencies were well below the local ion-plasma frequency. Surprisingly, the emissions consisted of electrostatic wave packets with shock- like envelopes, appearing repetitively at a \raisebox-0.5ex\textasciitilde1.5 Hz rate. This repetitiveness correlated and was in phase with low-frequency electromagnetic fluctuations. The emissions were associat ... Mozer, F.~S.; Vasko, I.~Y.; Verniero, J.~L.; Published by: \apjl Published on: sep YEAR: 2021 DOI: 10.3847/2041-8213/ac2259 On the Role of Solar Wind Expansion as a Source of Whistler Waves: Scattering of Suprathermal Electrons and Heat Flux Regulation in the Inner Heliosphere The role of solar wind expansion in generating whistler waves is investigated using the EB-iPic3D code, which models solar wind expansion self-consistently within a fully kinetic semi-implicit approach. The simulation is initialized with an electron velocity distribution function modeled after observations of the Parker Solar Probe during its first perihelion at 0.166 au, consisting of a dense core and an antisunward strahl. This distribution function is initially stable with respect to kinetic instabilities. Expansion drive ... Micera, A.; Zhukov, A.~N.; opez, R.~A.; Boella, E.; Tenerani, A.; Velli, M.; Lapenta, G.; Innocenti, M.~E.; Published by: \apj Published on: sep YEAR: 2021 DOI: 10.3847/1538-4357/ac1067 The Evolution of Compressible Solar Wind Turbulence in the Inner Heliosphere: PSP, THEMIS, and MAVEN Observations The first computations of the compressible energy transfer rate from \raisebox-0.5ex\textasciitilde0.2 up to \raisebox-0.5ex\textasciitilde1.7 au is obtained using Parker Solar Probe (PSP), Time History of Events and Macroscale Interactions during Substorms (THEMIS), and Mars Atmosphere and Volatile EvolutioN (MAVEN) observations. Using a recently derived exact relation for isothermal magnetohydrodynamics turbulence, the compressible energy cascade rate, \ensuremath\varepsilon$_C$, is computed for hundred of events at differ ... es, Andr\; Sahraoui, F.; Hadid, L.~Z.; Huang, S.~Y.; Romanelli, N.; Galtier, S.; DiBraccio, G.; Halekas, J.; Published by: \apj Published on: sep YEAR: 2021 DOI: 10.3847/1538-4357/ac0af5 Exploring the Solar Wind from Its Source on the Corona into the Inner Heliosphere during the First Solar Orbiter-Parker Solar Probe Quadrature This Letter addresses the first Solar Orbiter (SO)-Parker Solar Probe (PSP) quadrature, occurring on 2021 January 18 to investigate the evolution of solar wind from the extended corona to the inner heliosphere. Assuming ballistic propagation, the same plasma volume observed remotely in the corona at altitudes between 3.5 and 6.3 solar radii above the solar limb with the Metis coronagraph on SO can be tracked to PSP, orbiting at 0.1 au, thus allowing the local properties of the solar wind to be linked to the coronal source re ... Telloni, Daniele; Andretta, Vincenzo; Antonucci, Ester; Bemporad, Alessandro; Capuano, Giuseppe; Fineschi, Silvano; Giordano, Silvio; Habbal, Shadia; Perrone, Denise; Pinto, Rui; Sorriso-Valvo, Luca; Spadaro, Daniele; Susino, Roberto; Woodham, Lloyd; Zank, Gary; Romoli, Marco; Bale, Stuart; Kasper, Justin; Auchère, Fr\; Bruno, Roberto; Capobianco, Gerardo; Case, Anthony; Casini, Chiara; Casti, Marta; Chioetto, Paolo; Corso, Alain; Da Deppo, Vania; De Leo, Yara; de Wit, Thierry; Frassati, Federica; Frassetto, Fabio; Goetz, Keith; Guglielmino, Salvo; Harvey, Peter; Heinzel, Petr; Jerse, Giovanna; Korreck, Kelly; Landini, Federico; Larson, Davin; Liberatore, Alessandro; Livi, Roberto; MacDowall, Robert; Magli, Enrico; Malaspina, David; Massone, Giuseppe; Messerotti, Mauro; Moses, John; Naletto, Giampiero; Nicolini, Gianalfredo; o, Giuseppe; Panasenco, Olga; Pancrazzi, Maurizio; Pelizzo, Maria; Pulupa, Marc; Reale, Fabio; Romano, Paolo; Sasso, Clementina; Schühle, Udo; Stangalini, Marco; Stevens, Michael; Strachan, Leonard; Straus, Thomas; Teriaca, Luca; Uslenghi, Michela; Velli, Marco; Verscharen, Daniel; Volpicelli, Cosimo; Whittlesey, Phyllis; Zangrilli, Luca; Zimbardo, Gaetano; Zuppella, Paola; Published by: \apjl Published on: oct YEAR: 2021 DOI: 10.3847/2041-8213/ac282f Evolution of Switchbacks in the Inner Heliosphere We analyze magnetic field data from the first six encounters of Parker Solar Probe, three Helios fast streams and two Ulysses south polar passes covering heliocentric distances 0.1 \ensuremath\lesssim R \ensuremath\lesssim 3 au. We use this data set to statistically determine the evolution of switchbacks of different periods and amplitudes with distance from the Sun. We compare the radial evolution of magnetic field variances with that of the mean square amplitudes of switchbacks, and quantify the radial evolution of the cum ... Tenerani, Anna; Sioulas, Nikos; Matteini, Lorenzo; Panasenco, Olga; Shi, Chen; Velli, Marco; Published by: \apjl Published on: oct YEAR: 2021 DOI: 10.3847/2041-8213/ac2606 Ambipolar Electric Field and Potential in the Solar Wind Estimated from Electron Velocity Distribution Functions The solar wind escapes from the solar corona and is accelerated, over a short distance, to its terminal velocity. The energy balance associated with this acceleration remains poorly understood. To quantify the global electrostatic contribution to the solar wind dynamics, we empirically estimate the ambipolar electric field (E$_\ensuremath\parallel$) and potential (\ensuremath\Phi$_r,\ensuremath\infty$). We analyze electron velocity distribution functions (VDFs) measured in the near-Sun solar wind between 20.3 R$_S$and 85.3 ... Ber\vci\vc, Laura; c, Milan; Halekas, Jasper; Landi, Simone; Owen, Christopher; Verscharen, Daniel; Larson, Davin; Whittlesey, Phyllis; Badman, Samuel; Bale, Stuart.; Case, Anthony; Goetz, Keith; Harvey, Peter; Kasper, Justin; Korreck, Kelly; Livi, Roberto; MacDowall, Robert; Malaspina, David; Pulupa, Marc; Stevens, Michael; Published by: \apj Published on: nov YEAR: 2021 DOI: 10.3847/1538-4357/ac1f1c A powerful machine learning technique to extract proton core, beam, and \ensuremath\alpha-particle parameters from velocity distribution functions in space plasmas Context. The analysis of the thermal part of velocity distribution functions (VDFs) is fundamentally important for understanding the kinetic physics that governs the evolution and dynamics of space plasmas. However, calculating the proton core, beam, and \ensuremath\alpha-particle parameters for large data sets of VDFs is a time-consuming and computationally demanding process that always requires supervision by a human expert. \ Aims: We developed a machine learning tool that can extract proton core, beam, and \ensuremath\al ... Vech, D.; Stevens, M.~L.; Paulson, K.~W.; Malaspina, D.~M.; Case, A.~W.; Klein, K.~G.; Kasper, J.~C.; Published by: \aap Published on: jun YEAR: 2021 DOI: 10.1051/0004-6361/202141063 General Exact Law of Compressible Isentropic Magnetohydrodynamic Flows: Theory and Spacecraft Observations in the Solar Wind Various forms of exact laws governing magnetohydrodynamic (MHD) turbulence have been derived either in the incompressibility limit, or for isothermal compressible flows. Here we propose a more general method that allows us to obtain such laws for any turbulent isentropic flow (i.e., constant entropy). We demonstrate that the known MHD exact laws (incompressible and isothermal) and the new (polytropic) one can be obtained as specific cases of the general law when the corresponding closure equation is stated. We also recover a ... Simon, P.; Sahraoui, F.; Published by: \apj Published on: jul YEAR: 2021 DOI: 10.3847/1538-4357/ac0337 Turbulent Generation of Magnetic Switchbacks in the Alfv\ enic Solar Wind One of the most important early results from the Parker Solar Probe (PSP) is the ubiquitous presence of magnetic switchbacks, whose origin is under debate. Using a three-dimensional direct numerical simulation of the equations of compressible magnetohydrodynamics from the corona to 40 solar radii, we investigate whether magnetic switchbacks emerge from granulation-driven Alfv\ en waves and turbulence in the solar wind. The simulated solar wind is an Alfv\ enic slow-solar- wind stream with a radial profile consistent with var ... Shoda, Munehito; Chandran, Benjamin; Cranmer, Steven; Published by: \apj Published on: jul YEAR: 2021 DOI: 10.3847/1538-4357/abfdbc Analysis of Magnetohydrodynamic Perturbations in the Radial-field Solar Wind from Parker Solar Probe Observations We report analysis of sub-Alfv\ enic magnetohydrodynamic (MHD) perturbations in the low-\ensuremath\beta radial-field solar wind employing the Parker Solar Probe spacecraft data from 2018 October 31 to November 12. We calculate wavevectors using the singular value decomposition method and separate MHD perturbations into three eigenmodes (Alfv\ en, fast, and slow modes) to explore the properties of sub-Alfv\ enic perturbations and the role of compressible perturbations in solar wind heating. The MHD perturbations show a high ... Zhao, S.~Q.; Yan, Huirong; Liu, Terry; Liu, Mingzhe; Shi, Mijie; Published by: \apj Published on: dec YEAR: 2021 DOI: 10.3847/1538-4357/ac2ffe A Solar Source of Alfv\ enic Magnetic Field Switchbacks: In Situ Remnants of Magnetic Funnels on Supergranulation Scales One of the striking observations from the Parker Solar Probe (PSP) spacecraft is the prevalence in the inner heliosphere of large amplitude, Alfv\ enic magnetic field reversals termed switchbacks. These$\delta B_R/B\sim \mathcal O (1$) fluctuations occur over a range of timescales and in patches separated by intervals of quiet, radial magnetic field. We use measurements from PSP to demonstrate that patches of switchbacks are localized within the extensions of plasma structures originating at the base of the corona. These ... Bale, S.~D.; Horbury, T.~S.; Velli, M.; Desai, M.~I.; Halekas, J.~S.; McManus, M.~D.; Panasenco, O.; Badman, S.~T.; Bowen, T.~A.; Chandran, B.~D.~G.; Drake, J.~F.; Kasper, J.~C.; Laker, R.; Mallet, A.; Matteini, L.; Phan, T.~D.; Raouafi, N.~E.; Squire, J.; Woodham, L.~D.; Woolley, T.; Published by: \apj Published on: dec YEAR: 2021 DOI: 10.3847/1538-4357/ac2d8c Large-scale Structure and Turbulence Transport in the Inner Solar Wind: Comparison of Parker Solar Probe s First Five Orbits with a Global 3D Reynolds-averaged MHD Model Simulation results from a global magnetohydrodynamic model of the solar corona and solar wind are compared with Parker Solar Probe (PSP) observations during its first five orbits. The fully three- dimensional model is based on Reynolds-averaged mean-flow equations coupled with turbulence-transport equations. The model includes the effects of electron heat conduction, Coulomb collisions, turbulent Reynolds stresses, and heating of protons and electrons via a turbulent cascade. Turbulence-transport equations for average turbul ... Chhiber, Rohit; Usmanov, Arcadi; Matthaeus, William; Goldstein, Melvyn; Published by: \apj Published on: dec YEAR: 2021 DOI: 10.3847/1538-4357/ac1ac7 Geometry of Magnetic Fluctuations near the Sun from the Parker Solar Probe Solar wind magnetic fluctuations exhibit anisotropy due to the presence of a mean magnetic field in the form of the Parker spiral. Close to the Sun, direct measurements were not available until the recently launched Parker Solar Probe (PSP) mission. The nature of the anisotropy and geometry of the magnetic fluctuations play a fundamental role in dissipation processes and in the transport of energetic particles in space. Using PSP data, we present measurements of the geometry and anisotropy of the inner heliosphere magnetic f ... Bandyopadhyay, R.; McComas, D.~J.; Published by: \apj Published on: dec YEAR: 2021 DOI: 10.3847/1538-4357/ac3486 The angular-momentum flux in the solar wind observed during Solar Orbiter s first orbit \ Aims: We present the first measurements of the angular- momentum flux in the solar wind recorded by the Solar Orbiter spacecraft. Our aim is to validate these measurements to support future studies of the Sun s angular-momentum loss. \ Methods: We combined 60-min averages of the proton bulk moments and the magnetic field measured by the Solar Wind Analyser and the magnetometer onboard Solar Orbiter. We calculated the angular-momentum flux per solid-angle element using data from the first orbit of the mission s cruise phase ... Verscharen, Daniel; Stansby, David; Finley, Adam; Owen, Christopher; Horbury, Timothy; Maksimovic, Milan; Velli, Marco; Bale, Stuart; Louarn, Philippe; Fedorov, Andrei; Bruno, Roberto; Livi, Stefano; Khotyaintsev, Yuri; Vecchio, Antonio; Lewis, Gethyn; Anekallu, Chandrasekhar; Kelly, Christopher; Watson, Gillian; Kataria, Dhiren; Brien, Helen; Evans, Vincent; Angelini, Virginia; SWA, MAG; Teams, RPW; Published by: \aap Published on: dec YEAR: 2021 DOI: 10.1051/0004-6361/202140956 Solar wind current sheets and deHoffmann-Teller analysis. First results from Solar Orbiter s DC electric field measurements Context. Solar Orbiter was launched on 10 February 2020 with the purpose of investigating solar and heliospheric physics using a payload of instruments designed for both remote and in situ studies. Similar to the recently launched Parker Solar Probe, and unlike earlier missions, Solar Orbiter carries instruments designed to measure low-frequency DC electric fields. \ Aims: In this paper, we assess the quality of the low-frequency DC electric field measured by the Radio and Plasma Waves instrument (RPW) on Solar Orbiter. In p ... Steinvall, K.; Khotyaintsev, Yu.; Cozzani, G.; Vaivads, A.; Yordanova, E.; Eriksson, A.~I.; Edberg, N.~J.~T.; Maksimovic, M.; Bale, S.~D.; Chust, T.; Krasnoselskikh, V.; Kretzschmar, M.; Lorfèvre, E.; Plettemeier, D.; Sou\vcek, J.; Steller, M.; ak, \vS.; Vecchio, A.; Horbury, T.~S.; Brien, H.; Evans, V.; Fedorov, A.; Louarn, P.; enot, V.; e, Andr\; Lavraud, B.; Rouillard, A.~P.; Owen, C.~J.; Published by: \aap Published on: dec YEAR: 2021 DOI: 10.1051/0004-6361/202140855 Large Amplitude Switchback Turbulence: Possible Magnetic Velocity Alignment Structures Switchbacks are widely acknowledged phenomena observed by the Parker Solar Probe and appear to occur in patches. Previous studies focused on the fluctuations at the magnetic reversals. However, the nature of the fluctuations inside the switchbacks remains unknown. Here we utilize the magnetic field data and plasma data measured by the Parker Solar Probe in the first four encounters. We investigate the fluctuations in the switchback intervals of 100 s with$B_R 0\$ at every instant and compare them to the fluctuations in the n ... Wu, Honghong; Tu, Chuanyi; Wang, Xin; Yang, Liping; Published by: The Astrophysical Journal      Published on: 06/2021 YEAR: 2021     DOI: 10.3847/1538-4357/abec6c Applicability of Taylor s hypothesis during Parker Solar Probe perihelia We investigate the validity of Taylor s hypothesis (TH) in the analysis of velocity and magnetic field fluctuations in Alfvénic solar wind streams measured by Parker Solar Probe (PSP) during the first four encounters. The analysis is based on a recent model of the spacetime correlation of magnetohydrodynamic (MHD) turbulence, which has been validated in high-resolution numerical simulations of strong reduced MHD turbulence. We use PSP velocity and magnetic field measurements from 24 h intervals selected from each of the fir ... Perez, Jean; Bourouaine, Sofiane; Chen, Christopher; Raouafi, Nour; Published by: Astronomy and Astrophysics      Published on: 06/2021 YEAR: 2021     DOI: 10.1051/0004-6361/202039879

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