Found 221 results
Author Title Type [ Year(Asc)]
2020
Authors: Szalay J. R., Pokorný P., Bale S. D., Christian E. R., Goetz K., et al.
Title: The Near-Sun Dust Environment: Initial Observations from Parker Solar Probe
Abstract:

The Parker Solar Probe (PSP) spacecraft has flown into the densest, previously unexplored, innermost region of our solar system’s zodiacal cloud. While PSP does not have a dedicated dust detector, multiple instruments on the spacecraft are sensitive to the effects of meteoroid bombardment. Here, we discuss measurements taken during PSP’s second orbit and compare them to models of the zodiacal cloud’s dust distribution. Comparing the radial impact rate trends and the timing and location of a dust impact to an energetic particle detector, we find the impactor population to be consistent with dust grains on hyperbolic orbits escaping the solar system. Assuming PSP’s impact environment is dominated by hyperbolic impactors, the total quantity of dust ejected from our solar system is . . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 27 DOI: 10.3847/1538-4365/ab50c1 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab50c1
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Authors: Němeček Zdeněk, Ďurovcová Tereza, Šafránková Jana, Richardson John D., Šimůnek Jiří, et al.
Title: (Non)radial Solar Wind Propagation through the Heliosphere
Abstract:

The solar wind nonradial velocity components observed beyond the Alfvén point are usually attributed to waves, the interaction of different streams, or other transient phenomena. However, Earth-orbiting spacecraft as well as monitors at L1 indicate systematic deviations of the wind velocity from the radial direction. Since these deviations are of the order of several degrees, the calibration of the instruments is often questioned. This paper investigates for the first time the evolution of nonradial components of the solar wind flow along the path from ≍0.17 to 10 au. A comparison of observations at 1 au with those closer to or farther from the Sun based on measurements of many spacecraft at different locations in the heliosphere (Parker Solar Probe, Helios 1 and 2, Wind, Advanced Co. . .
Date: 07/2020 Publisher: The Astrophysical Journal Pages: L39 DOI: 10.3847/2041-8213/ab9ff7 Available at: https://iopscience.iop.org/article/10.3847/2041-8213/ab9ff7https://iopscience.iop.org/article/10.3847/2041-8213/ab9ff7
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Authors: Roberts Aaron, Karimabadi Homa, Sipes Tamara, Ko Yuan-Kuen, and Lepri Susan
Title: Objectively Determining States of the Solar Wind Using Machine Learning
Abstract:

Conclusively determining the states of the solar wind will aid in tracing the origins of those states to the Sun, and in the process help to find the wind’s origin and acceleration mechanism(s). Prior studies have characterized the various states of the wind, making lists that are only partially based on objective criteria; different approaches obtain substantially different results. To uncover the unbiased states of the solar wind, we use "k-means clustering"—an unsupervised machine learning method—including constructed multipoint variables. The method allows exploration of different descriptive state variables and numbers of fundamental states (clusters). We show that the clusters reveal structures similar to those found by more ad hoc means, including coronal hole wind, interpl. . .
Date: 02/2020 Publisher: The Astrophysical Journal Pages: 153 DOI: 10.3847/1538-4357/ab5a7a Available at: https://iopscience.iop.org/article/10.3847/1538-4357/ab5a7a
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Authors: Bandyopadhyay Riddhi, Matthaeus W. H., Parashar T. N., Chhiber R., Ruffolo D., et al.
Title: Observations of Energetic-particle Population Enhancements along Intermittent Structures near the Sun from the Parker Solar Probe
Abstract:

Observations at 1 au have confirmed that enhancements in measured energetic-particle (EP) fluxes are statistically associated with "rough" magnetic fields, i.e., fields with atypically large spatial derivatives or increments, as measured by the Partial Variance of Increments (PVI) method. One way to interpret this observation is as an association of the EPs with trapping or channeling within magnetic flux tubes, possibly near their boundaries. However, it remains unclear whether this association is a transport or local effect; i.e., the particles might have been energized at a distant location, perhaps by shocks or reconnection, or they might experience local energization or re-acceleration. The Parker Solar Probe (PSP), even in its first two orbits, offers a unique opportunity to study. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 61 DOI: 10.3847/1538-4365/ab6220 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab6220
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Authors: Qudsi R. A., Maruca B. A., Matthaeus W. H., Parashar T. N., Bandyopadhyay Riddhi, et al.
Title: Observations of Heating along Intermittent Structures in the Inner Heliosphere from PSP Data
Abstract:

The solar wind proton temperature at 1 au has been found to be correlated with small-scale intermittent magnetic structures, i.e., regions with enhanced temperature are associated with coherent structures, such as current sheets. Using Parker Solar Probe data from the first encounter, we study this association using measurements of the radial proton temperature, employing the partial variance of increments (PVI) technique to identify intermittent magnetic structures. We observe that the probability density functions of high PVI events have higher median temperatures than those with lower PVI. The regions in space where PVI peaks were also locations that had enhanced temperatures when compared with similar regions, suggesting a heating mechanism in the young solar wind that is associated. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 46 DOI: 10.3847/1538-4365/ab5c19 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5c19
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Authors: Leske R. A., Christian E. R., Cohen C. M. S., Cummings A. C., Davis A. J., et al.
Title: Observations of the 2019 April 4 Solar Energetic Particle Event at the Parker Solar Probe
Abstract:

A solar energetic particle event was detected by the Integrated Science Investigation of the Sun (IS☉IS) instrument suite on Parker Solar Probe (PSP) on 2019 April 4 when the spacecraft was inside of 0.17 au and less than 1 day before its second perihelion, providing an opportunity to study solar particle acceleration and transport unprecedentedly close to the source. The event was very small, with peak 1 MeV proton intensities of ̃0.3 particles (cm2 sr s MeV)-1, and was undetectable above background levels at energies above 10 MeV or in particle detectors at 1 au. It was strongly anisotropic, with intensities flowing outward from the Sun up to 30 times greater than those flowing inward persisting throughout the event. Temporal association between particle incre. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 35 DOI: 10.3847/1538-4365/ab5712 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5712
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Authors: Verniero J. L., Larson D. E., Livi R., Rahmati A., McManus M. D., et al.
Title: Parker Solar Probe Observations of Proton Beams Simultaneous with Ion-scale Waves
Abstract:

Parker Solar Probe (PSP), NASA’s latest and closest mission to the Sun, is on a journey to investigate fundamental enigmas of the inner heliosphere. This paper reports initial observations made by the Solar Probe Analyzer for Ions (SPAN-I), one of the instruments in the Solar Wind Electrons Alphas and Protons instrument suite. We address the presence of secondary proton beams in concert with ion-scale waves observed by FIELDS, the electromagnetic fields instrument suite. We show two events from PSP’s second orbit that demonstrate signatures consistent with wave-particle interactions. We showcase 3D velocity distribution functions (VDFs) measured by SPAN-I during times of strong wave power at ion scales. From an initial instability analysis, we infer that the VDFs departed far enough. . .
Date: 05/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 5 DOI: 10.3847/1538-4365/ab86af Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab86afhttps
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Authors: Yang Zhongwei, Liu Ying D., Matsukiyo Shuichi, Lu Quanming, Guo Fan, et al.
Title: PIC Simulations of Microinstabilities and Waves at Near-Sun Solar Wind Perpendicular Shocks: Predictions for Parker Solar Probe and Solar Orbiter
Abstract:

Microinstabilities and waves excited at moderate-Mach-number perpendicular shocks in the near-Sun solar wind are investigated by full particle-in-cell simulations. By analyzing the dispersion relation of fluctuating field components directly issued from the shock simulation, we obtain key findings concerning wave excitations at the shock front: (1) at the leading edge of the foot, two types of electrostatic (ES) waves are observed. The relative drift of the reflected ions versus the electrons triggers an electron cyclotron drift instability (ECDI) that excites the first ES wave. Because the bulk velocity of gyro-reflected ions shifts to the direction of the shock front, the resulting ES wave propagates oblique to the shock normal. Immediately, a fraction of incident electrons are accele. . .
Date: 09/2020 Publisher: The Astrophysical Journal Pages: L24 DOI: 10.3847/2041-8213/abaf59 Available at: https://iopscience.iop.org/article/10.3847/2041-8213/abaf59https://iopscience.iop.org/article/10.3847/2041-8213/abaf59/pdf
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Authors: Meyer-Vernet Nicole, and Moncuquet Michel
Title: Plasma Waves in Space: The Importance of Properly Accounting for the Measuring Device
Abstract:

Electric fields are generally measured or calculated using two intuitive assumptions: (1) the electric field equals the voltage divided by the antenna length when the antenna is electromagnetically short (2) the antenna responds best to electric field along its length. Both assumptions are often incorrect for electrostatic fields because they scale as the Debye length or as the electron gyroradius, which may be smaller than the antenna length. Taking into account this little-known fact enables us to complete or correct several recent papers on plasma spontaneous fluctuations in various solar system environments.


Date: 03/2020 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2019JA027723 Available at: https://onlinelibrary.wiley.com/doi/abs/10.1029/2019JA027723
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Authors: Malaspina David M., Halekas Jasper, Berčič Laura, Larson Davin, Whittlesey Phyllis, et al.
Title: Plasma Waves near the Electron Cyclotron Frequency in the Near-Sun Solar Wind
Abstract:

Data from the first two orbits of the Sun by Parker Solar Probe reveal that the solar wind sunward of 50 solar radii is replete with plasma waves and instabilities. One of the most prominent plasma wave power enhancements in this region appears near the electron cyclotron frequency (fce). Most of this wave power is concentrated in electric field fluctuations near 0.7 fce and fce, with strong harmonics of both frequencies extending above fce. At least two distinct, often concurrent, wave modes are observed, preliminarily identified as electrostatic whistler-mode waves and electron Bernstein waves. Wave intervals range in duration from a few seconds to hours. Both the amplitudes and number of detections of these near-fce waves increas. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 21 DOI: 10.3847/1538-4365/ab4c3b Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab4c3b
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Authors: Nicolaou Georgios, Livadiotis George, Wicks Robert T., Verscharen Daniel, and Maruca Bennett A.
Title: Polytropic Behavior of Solar Wind Protons Observed by Parker Solar Probe
Abstract:

A polytropic process describes the transition of a fluid from one state to another through a specific relationship between the fluid density and temperature. The value of the polytropic index that governs this relationship determines the heat transfer and the effective degrees of freedom during a specific process. In this study, we analyze solar wind proton plasma measurements, obtained by the Faraday cup instrument on board the Parker Solar Probe. We examine the large-scale variations of the proton plasma density and temperature within the inner heliosphere explored by the spacecraft. We then address the polytropic behavior in the density and temperature fluctuations in short time intervals, which we analyze in order to derive the effective polytropic index of . . .
Date: 09/2020 Publisher: The Astrophysical Journal Pages: 26 DOI: 10.3847/1538-4357/abaaae Available at: https://iopscience.iop.org/article/10.3847/1538-4357/abaaaehttps://iopscience.iop.org/article/10.3847/1538-4357/abaaae/pdf
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Authors: Kim T. K., Pogorelov N. V., Arge C. N., Henney C. J., Jones-Mecholsky S. I., et al.
Title: Predicting the Solar Wind at the Parker Solar Probe Using an Empirically Driven MHD Model
Abstract:

Since its launch on 2018 August 12, Parker Solar Probe (PSP) has completed its first and second orbits around the Sun, having reached down to 35.7 solar radii at each perihelion. In anticipation of the exciting new data at such unprecedented distances, we have simulated the global 3D heliosphere using an MHD model coupled with a semi-empirical coronal model using the best available photospheric magnetograms as input. We compare our heliospheric MHD simulation results with in situ measurements along the PSP trajectory from its launch to the completion of the second orbit, with particular emphasis on the solar wind structure around the first two solar encounters. Furthermore, we show our model prediction for the third perihelion, which occurred on 2019 September 1. Comparison of the MHD r. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 40 DOI: 10.3847/1538-4365/ab58c9 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab58c9
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Authors: Hibberd Adam, Hein Andreas M., and Eubanks Marshall
Title: Project Lyra: Catching 1I/‘Oumuamua – Mission opportunities after 2024
Abstract:

In October 2017, the first interstellar object within our solar system was discovered. Today designated 1I/’Oumuamua, it shows characteristics that have never before been observed in a celestial body. Due to these characteristics, an in-situ investigation of 1I would be of extraordinary scientific value. Previous studies have demonstrated that a mission to 1I/’Oumuamua is feasible using current and near-term technologies, however, with an anticipated launch date of 2020-2021. This is too soon to be realistic. This paper aims at addressing the question of the feasibility of a mission to 1I/’Oumuamua in 2024 and beyond. Using the OITS trajectory simulation tool, various scenarios are analyzed, including a powered Jupiter flyby and Solar Oberth maneuver, a Jupiter powered flyby, and . . .
Date: 05/2020 Publisher: Acta Astronautica Pages: 136 - 144 DOI: 10.1016/j.actaastro.2020.01.018 Available at: https://linkinghub.elsevier.com/retrieve/pii/S0094576520300291
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Authors: Desai M. I., Mitchell D. G., Szalay J. R., Roelof E. C., Giacalone J., et al.
Title: Properties of Suprathermal-through-energetic He Ions Associated with Stream Interaction Regions Observed over the Parker Solar Probe ’s First Two Orbits
Abstract:

The Integrated Science Investigation of the Sun (IS☉IS) suite on board NASA's Parker Solar Probe (PSP) observed six distinct enhancements in the intensities of suprathermal-through-energetic (∼0.03─3 MeV nucleon−1) He ions associated with corotating or stream interaction regions (CIR or SIR) during its first two orbits. Our results from a survey of the time histories of the He intensities, spectral slopes, and anisotropies and the event-averaged energy spectra during these events show the following: (1) In the two strongest enhancements, seen at 0.35 and 0.85 au, the higher-energy ions arrive and maximize later than those at lower energies. In the event seen at 0.35 au, the He ions arrive when PSP was away from the SIR trailing edge and entered the rarefaction region . . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 56 DOI: 10.3847/1538-4365/ab65ef Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab65efhttps://iopscience.iop.org/article/10.3847/1538-4365/ab65ef/
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Authors: Duan Die, Bowen Trevor A., Chen Christopher H. K., Mallet Alfred, He Jiansen, et al.
Title: The Radial Dependence of Proton-scale Magnetic Spectral Break in Slow Solar Wind during PSP Encounter 2
Abstract:

Magnetic field fluctuations in the solar wind are commonly observed to follow a power-law spectrum. Near proton-kinetic scales, a spectral break occurs that is commonly interpreted as a transition to kinetic turbulence. However, this transition is not yet entirely understood. By studying the scaling of the break with various plasma properties, it may be possible to constrain the processes leading to the onset of kinetic turbulence. Using data from the Parker Solar Probe, we measure the proton-scale break over a range of heliocentric distances, enabling a measurement of the transition from inertial to kinetic-scale turbulence under various plasma conditions. We find that the break frequency fb increases as the heliocentric distance r decreases in the slow solar wind following . . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 55 DOI: 10.3847/1538-4365/ab672d Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab672d
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Authors: Rouillard Alexis P., Kouloumvakos Athanasios, Vourlidas Angelos, Kasper Justin, Bale Stuart, et al.
Title: Relating Streamer Flows to Density and Magnetic Structures at the Parker Solar Probe
Abstract:

The physical mechanisms that produce the slow solar wind are still highly debated. Parker Solar Probe’s (PSP’s) second solar encounter provided a new opportunity to relate in situ measurements of the nascent slow solar wind with white-light images of streamer flows. We exploit data taken by the Solar and Heliospheric Observatory, the Solar TErrestrial RElations Observatory (STEREO), and the Wide Imager on Solar Probe to reveal for the first time a close link between imaged streamer flows and the high-density plasma measured by the Solar Wind Electrons Alphas and Protons (SWEAP) experiment. We identify different types of slow winds measured by PSP that we relate to the spacecraft’s magnetic connectivity (or not) to streamer flows. SWEAP measured high-density and highly variable pla. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 37 DOI: 10.3847/1538-4365/ab579a Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab579a
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Authors: Réville Victor, Velli Marco, Panasenco Olga, Tenerani Anna, Shi Chen, et al.
Title: The Role of Alfvén Wave Dynamics on the Large-scale Properties of the Solar Wind: Comparing an MHD Simulation with Parker Solar Probe E1 Data
Abstract:

During Parker Solar Probe’s first orbit, the solar wind plasma was observed in situ closer than ever before, the perihelion on 2018 November 6 revealing a flow that is constantly permeated by large-amplitude Alfvénic fluctuations. These include radial magnetic field reversals, or switchbacks, that seem to be a persistent feature of the young solar wind. The measurements also reveal a very strong, unexpected, azimuthal velocity component. In this work, we numerically model the solar corona during this first encounter, solving the MHD equations and accounting for Alfvén wave transport and dissipation. We find that the large-scale plasma parameters are well reproduced, allowing the computation of the solar wind sources at Probe with confidence. We try to understand the dynamical nature. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 24 DOI: 10.3847/1538-4365/ab4fef Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab4fef
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Authors: Alberti Tommaso, Laurenza Monica, Consolini Giuseppe, Milillo Anna, Marcucci Maria Federica, et al.
Title: On the Scaling Properties of Magnetic-field Fluctuations through the Inner Heliosphere
Abstract:

Although the interplanetary magnetic-field variability has been extensively investigated in situ using data from several space missions, newly launched missions providing high-resolution measures and approaching the Sun offer the possibility to study the multiscale variability in the innermost solar system. Here, using Parker Solar Probe measurements, we investigate the scaling properties of solar wind magnetic-field fluctuations at different heliocentric distances. The results show a clear transition at distances close to say 0.4 au. Closer to the Sun fluctuations show af(-3/2)frequency power spectra and regular scaling properties, while for distances larger than 0.4 au fluctuations show a Kolmogorov spectrumf(-5/3)and are characterized by anomal. . .
Date: 10/2020 Publisher: The Astrophysical Journal Pages: 84 DOI: 10.3847/1538-4357/abb3d2 Available at: https://iopscience.iop.org/article/10.3847/1538-4357/abb3d2https://iopscience.iop.org/article/10.3847/1538-4357/abb3d2/pdf
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Authors: Schwadron N. A., Bale S., Bonnell J., Case A., Christian E. R., et al.
Title: Seed Population Preconditioning and Acceleration Observed by the Parker Solar Probe
Abstract:

A series of solar energetic particle (SEP) events was observed by the Integrated Science Investigation of the Sun (IS☉IS) on the Parker Solar Probe (PSP) during the period from 2019 April 18 through 24. The PSP spacecraft was located near 0.48 au from the Sun on Parker spiral field lines that projected out to 1 au within ̃25° of the near-Earth spacecraft. These SEP events, though small compared to historically large SEP events, were among the largest observed thus far in the PSP mission and provide critical information about the space environment inside 1 au during SEP events. During this period, the Sun released multiple coronal mass ejections (CMEs). One of these CMEs observed was initiated on 2019 April 20 at 01:25 UTC, and the interplanetary CME (ICME) propagated out and passed . . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 33 DOI: 10.3847/1538-4365/ab5527 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5527
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Authors: Strauss R. D., Dresing N., Kollhoff A., and Brüdern M.
Title: On the Shape of SEP Electron Spectra: The Role of Interplanetary Transport
Abstract:

We address the effect of particle scattering on the energy spectra of solar energetic electron events using (I) an observational and (II) a modeling approach. (I) We statistically study observations of the STEREO spacecraft, using directional electron measurements made with the Solar Electron and Proton Telescope in the range of 45-425 keV. We compare the energy spectra of the anti-Sunward propagating beam with that of the backward-scattered population and find that, on average, the backward-scattered population shows a harder spectrum with the effect being stronger at higher energies. (II) We use a numerical solar energetic particle (SEP) transport model to simulate the effect of particle scattering (both in terms of pitch angle and perpendicular to the mean field) on the spectrum. We . . .
Date: 07/2020 Publisher: The Astrophysical Journal Pages: 24 DOI: 10.3847/1538-4357/ab91b0 Available at: https://iopscience.iop.org/article/10.3847/1538-4357/ab91b0https://iopscience.iop.org/article/10.3847/1538-4357/ab91b0/
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Authors: Horbury Timothy S., Woolley Thomas, Laker Ronan, Matteini Lorenzo, Eastwood Jonathan, et al.
Title: Sharp Alfvénic Impulses in the Near-Sun Solar Wind
Abstract:

Measurements of the near-Sun solar wind by the Parker Solar Probe have revealed the presence of large numbers of discrete Alfvénic impulses with an anti-sunward sense of propagation. These are similar to those previously observed near 1 au, in high speed streams over the Sun’s poles and at 60 solar radii. At 35 solar radii, however, they are typically shorter and sharper than seen elsewhere. In addition, these spikes occur in "patches" and there are also clear periods within the same stream when they do not occur; the timescale of these patches might be related to the rate at which the spacecraft magnetic footpoint tracks across the coronal hole from which the plasma originated. While the velocity fluctuations associated with these spikes are typically under 100 km s-1, du. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 45 DOI: 10.3847/1538-4365/ab5b15 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5b15
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Authors: Ruffolo D., Matthaeus W. H., Chhiber R., Usmanov A. V., Yang Y., et al.
Title: Shear-driven Transition to Isotropically Turbulent Solar Wind Outside the Alfvén Critical Zone
Abstract:

Motivated by prior remote observations of a transition from striated solar coronal structures to more isotropic "flocculated" fluctuations, we propose that the dynamics of the inner solar wind just outside the Alfven critical zone, and in the vicinity of the first beta = 1 surface, is powered by the relative velocities of adjacent coronal magnetic flux tubes. We suggest that large-amplitude flow contrasts are magnetically constrained at lower altitude but shear-driven dynamics are triggered as such constraints are released above the Alfven critical zone, as suggested by global magnetohy drodynamic (MHD) simulations that include self-consistent turbulence transport. We argue that this dynamical evolution accounts for features observed by Parker Solar Pr. . .
Date: 10/2020 Publisher: The Astrophysical Journal Pages: 94 DOI: 10.3847/1538-4357/abb594 Available at: https://iopscience.iop.org/article/10.3847/1538-4357/abb594https://iopscience.iop.org/article/10.3847/1538-4357/abb594/pdf
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Authors: Nisticò Giuseppe, Bothmer Volker, Vourlidas Angelos, Liewer Paulett C., Thernisien Arnaud F., et al.
Title: Simulating White-Light Images of Coronal Structures for Parker Solar Probe/WISPR: Study of the Total Brightness Profiles
Abstract:

The Wide-field Imager for Parker Solar Probe (WISPR) captures unprecedented white-light images of the solar corona and inner heliosphere. Thanks to the uniqueness of the Parker Solar Probe’s (PSP) orbit, WISPR is able to image "locally" coronal structures at high spatial and time resolutions. The observed plane of sky, however, rapidly changes because of the PSP’s high orbital speed. Therefore, the interpretation of the dynamics of the coronal structures recorded by WISPR is not straightforward. A first study, undertaken by Liewer et al. (Solar Phys.294, 93, 2019), shows how different coronal features (e.g., streamers, flux ropes) appear in the field-of-view of WISPR by means of raytracing simulations. In particular, they analyze the effects of the spatial resolution changes on both. . .
Date: 04/2020 Publisher: Solar Physics DOI: 10.1007/s11207-020-01626-y Available at: http://link.springer.com/10.1007/s11207-020-01626-yhttp
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Authors: Mitchell J. G., de Nolfo G. A., Hill M. E., Christian E. R., McComas D. J., et al.
Title: Small Electron Events Observed by Parker Solar Probe/IS⊙IS during Encounter 2
Abstract:

The current understanding of the characteristics of solar and inner heliospheric electron events is inferred almost entirely from observations made by spacecraft located at 1 astronomical unit (au). Previous observations within 1 au of the Sun, by the Helios spacecraft at similar to 0.3-1 au, indicate the presence of electron events that are not detected at 1 au or may have merged during transport from the Sun. Parker Solar Probe's close proximity to the Sun at perihelion provides an opportunity to make the closest measurements yet of energetic electron events. We present an overview of measurements of electrons with energies between similar to 17 keV and similar to 1 MeV made by the Parker Solar Probe Integrated Science Investigation of the . . .
Date: 10/2020 Publisher: The Astrophysical Journal Pages: 20 DOI: 10.3847/1538-4357/abb2a4 Available at: https://iopscience.iop.org/article/10.3847/1538-4357/abb2a4https://iopscience.iop.org/article/10.3847/1538-4357/abb2a4/pdf
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Authors: Hill M. E., Mitchell D. G., Allen R. C., de Nolfo G. A., Vourlidas A., et al.
Title: Small, Low-energy, Dispersive Solar Energetic Particle Events Observed by Parker Solar Probe
Abstract:

The Energetic Particle Instrument-Low Energy (EPI-Lo) experiment has detected several weak, low-energy (̃30-300 keV nucleon-1) solar energetic particle (SEP) events during its first two closest approaches to the Sun, providing a unique opportunity to explore the sources of low-energy particle acceleration. As part of the Parker Solar Probe (PSP) Integrated Science Investigation of the Sun (IS☉IS) suite, EPI-Lo was designed to investigate the physics of energetic particles; however, in the special lowest-energy "time-of-flight only" product used in this study, it also responds to solar photons in a subset of approximately sunward-looking apertures lacking special light-attenuating foils. During the first three perihelia, in a frame rotating with the Sun, PSP undergoes retro. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 65 DOI: 10.3847/1538-4365/ab643d Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab643
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