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2020
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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Authors: Adhikari L., Zank G. P., and Zhao L.-L.
Title: A Solar Coronal Hole and Fast Solar Wind Turbulence Model and First-orbit Parker Solar Probe (PSP) Observations
Abstract:

We propose a turbulence-driven solar wind model for a fast solar wind flow in an open coronal hole where the solar wind flow and the magnetic field are highly aligned. We compare the numerical results of our model with Parker Solar Probe measurements of the fast solar wind flow and find good agreement between them. We find that (1) the majority quasi-2D turbulence is mainly responsible for coronal heating, raising the temperature to about similar to 1(6) K within a few solar radii, which leads in turn to the acceleration of the solar wind; (2) the heating rate due to quasi-2D turbulence near the coronal base is larger than that due to nearly incompressible/slab turbulence; (3) the quasi-2D energy in forward-. . .
Date: 10/2020 Publisher: The Astrophysical Journal Pages: 102 DOI: 10.3847/1538-4357/abb132 Available at: https://iopscience.iop.org/article/10.3847/1538-4357/abb132https://iopscience.iop.org/article/10.3847/1538-4357/abb132/pdf
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Authors: Giacalone J., Mitchell D. G., Allen R. C., Hill M. E., McNutt R. L., et al.
Title: Solar Energetic Particles Produced by a Slow Coronal Mass Ejection at \~0.25 au
Abstract:

We present an analysis of Parker Solar Probe (PSP) IS☉IS observations of ̃30-300 keV n-1 ions on 2018 November 11 when PSP was about 0.25 au from the Sun. Five hours before the onset of a solar energetic particle (SEP) event, a coronal mass ejection (CME) was observed by STEREO-A/COR2, which crossed PSP about a day later. No shock was observed locally at PSP, but the CME may have driven a weak shock earlier. The SEP event was dispersive, with higher energy ions arriving before the lower energy ones. Timing suggests the particles originated at the CME when it was at ̃7.4R. SEP intensities increased gradually from their onset over a few hours, reaching a peak, and then decreased gradually before the CME arrived at PSP. The event was weak, having a very soft en. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 29 DOI: 10.3847/1538-4365/ab5221 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5221
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Authors: Kouloumvakos Athanasios, Vourlidas Angelos, Rouillard Alexis P., Roelof Edmond C., Leske Rick, et al.
Title: The Solar Origin of Particle Events Measured by Parker Solar Probe
Abstract:

During the second solar encounter phase of Parker Solar Probe (PSP), two small solar energetic particle (SEP) events were observed by the Integrated Science Investigation of the Sun, on 2019 April 2 and 4. At the time, PSP was approaching its second perihelion at a distance of ∼24.8 million kilometers from the solar center, it was in near-radial alignment with STEREO-A and in quadrature with Earth. During the two SEP events multiple narrow ejections and a streamer-blowout coronal mass ejection (SBO-CME) originated from a solar region situated eastward of PSP. We analyze remote-sensing observations of the solar corona, and model the different eruptions and how PSP was connected magnetically to the solar atmosphere to determine the possible origin of the two SEP events. We find that the. . .
Date: 08/2020 Publisher: The Astrophysical Journal Pages: 107 DOI: 10.3847/1538-4357/aba5a1 Available at: https://iopscience.iop.org/article/10.3847/1538-4357/aba5a1https://iopscience.iop.org/article/10.3847/1538-4357/aba5a1/
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Authors: Whittlesey Phyllis L., Larson Davin E., Kasper Justin C., Halekas Jasper, Abatcha Mamuda, et al.
Title: The Solar Probe ANalyzers—Electrons on the Parker Solar Probe
Abstract:

Electrostatic analyzers of different designs have been used since the earliest days of the space age, beginning with the very earliest solar-wind measurements made by Mariner 2 en route to Venus in 1962. The Parker Solar Probe (PSP) mission, NASA’s first dedicated mission to study the innermost reaches of the heliosphere, makes its thermal plasma measurements using a suite of instruments called the Solar Wind Electrons, Alphas, and Protons (SWEAP) investigation. SWEAP’s electron PSP Analyzer (Solar Probe ANalyzer-Electron (SPAN-E)) instruments are a pair of top-hat electrostatic analyzers on PSP that are capable of measuring the electron distribution function in the solar wind from 2 eV to 30 keV. For the first time, in situ measurements of thermal electrons provided by SPAN-E will . . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 74 DOI: 10.3847/1538-4365/ab7370 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab7370https://iopscience.iop.org/article/10.3847/1538-4365/ab7370/pdf
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Authors: Case A. W., Kasper Justin C., Stevens Michael L., Korreck Kelly E., Paulson Kristoff, et al.
Title: The Solar Probe Cup on the Parker Solar Probe
Abstract:

Solar Probe Cup (SPC) is a Faraday cup instrument on board NASA’s Parker Solar Probe (PSP) spacecraft designed to make rapid measurements of thermal coronal and solar wind plasma. The spacecraft is in a heliocentric orbit that takes it closer to the Sun than any previous spacecraft, allowing measurements to be made where the coronal and solar wind plasma is being heated and accelerated. The SPC instrument was designed to be pointed directly at the Sun at all times, allowing the solar wind (which is flowing primarily radially away from the Sun) to be measured throughout the orbit. The instrument is capable of measuring solar wind ions with an energy between 100 and 6000 V (protons with speeds from 139 to 1072 km s-1). It also measures electrons with an energy/charge between . . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 43 DOI: 10.3847/1538-4365/ab5a7b Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5a7b
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Authors: Finley Adam J., Matt Sean P., Réville Victor, Pinto Rui F., Owens Mathew, et al.
Title: The Solar Wind Angular Momentum Flux as Observed by Parker Solar Probe
Abstract:

he long-term evolution of the Sun's rotation period cannot be directly observed, and is instead inferred from trends in the measured rotation periods of other Sun-like stars. Assuming the Sun spins down as it ages, following rotation rate proportional to age(-1/2), requires the current solar angular momentum (AM) loss rate to be around 6 x 10(30)erg. Magnetohydrodynamic models, and previous observations of the solar wind (from the Helios and Wind spacecraft), generally predict a values closer to 1 x 10(30)erg or 3 x 10(30)erg, respectively. Recently, the Parker Solar Probe (PSP) observed tangential solar wind speeds as high as similar to 50 km s(-1)in a localized region of the inner heliosphere. If such rotational flows were prevalent th. . .
Date: 10/2020 Publisher: The Astrophysical Journal Pages: L4 DOI: 10.3847/2041-8213/abb9a5 Available at: https://iopscience.iop.org/article/10.3847/2041-8213/abb9a5https://iopscience.iop.org/article/10.3847/2041-8213/abb9a5/pdf
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Authors: Allen R. C., Lario D., Odstrcil D., Ho G. C., Jian L. K., et al.
Title: Solar Wind Streams and Stream Interaction Regions Observed by the Parker Solar Probe with Corresponding Observations at 1 au
Abstract:

Several fast solar wind streams and stream interaction regions (SIRs) were observed by the Parker Solar Probe (PSP) during its first orbit (2018 September-2019 January). During this time, several recurring SIRs were also seen at 1 au at both L1 (Advanced Composition Explorer (ACE) and Wind) and the location of the Solar Terrestrial Relations Observatory-Ahead (STEREO-A). In this paper, we compare four fast streams observed by PSP at different radial distances during its first orbit. For three of these fast stream events, measurements from L1 (ACE and Wind) and STEREO-A indicated that the fast streams were observed by both PSP and at least one of the 1 au monitors. Our associations are supported by simulations made by the ENLIL model driven by GONG-(ADAPT-)WSA, which allows us to context. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 36 DOI: 10.3847/1538-4365/ab578f Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab578f
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Authors: Korreck Kelly E., Szabo Adam, Chinchilla Teresa Nieves, Lavraud Benoit, Luhmann Janet, et al.
Title: Source and Propagation of a Streamer Blowout Coronal Mass Ejection Observed by the Parker Solar Probe
Abstract:

In the first orbit of the Parker Solar Probe (PSP), in situ thermal plasma and magnetic field measurements were collected as close as 35 RSun from the Sun, an environment that had not been previously explored. During the first orbit of PSP, the spacecraft flew through a streamer blowout coronal mass ejection (SBO-CME) on 2018 November 11 at 23:50 UT as it exited the science encounter. The SBO-CME on November 11 was directed away from the Earth and was not visible by L1 or Earth-based telescopes due to this geometric configuration. However, PSP and the STEREO-A spacecraft were able to make observations of this slow (v ≈ 380 km s-1) SBO-CME. Using the PSP data, STEREO-A images, and Wang-Sheeley-Arge model, the source region of the CME is found to be a helmet stream. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 69 DOI: 10.3847/1538-4365/ab6ff9 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab6ff9
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Authors: Zhao L.-L., Zank G. P., Adhikari L., Nakanotani M., Telloni D., et al.
Title: Spectral Features in Field-aligned Solar Wind Turbulence from Parker Solar Probe Observations
Abstract:

Parker Solar Probe (PSP) observed a large variety of Alfvénic fluctuations in the fast and slow solar wind flow during its two perihelia. The properties of Alfvénic solar wind turbulence have been studied for decades in the near-Earth environment. A spectral index of -5/3 or -2 for magnetic field fluctuations has been observed using spacecraft measurements, which can be explained by turbulence theories of nearly incompressible magnetohydrodynamics (NI MHD) or critical balance. In this study, a rigorous search of field-aligned solar wind is applied to PSP measurements for the first time, which yields two events in the apparently slow solar wind. The parallel spectra of the magnetic fluctuations in the inertial range show a k −5/3 ∥  k∥−5/3 power law. . .
Date: 08/2020 Publisher: The Astrophysical Journal Pages: 113 DOI: 10.3847/1538-4357/ab9b7e Available at: https://iopscience.iop.org/article/10.3847/1538-4357/ab9b7e
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Authors: Pulupa Marc, Bale Stuart D., Badman Samuel T., Bonnell J. W., Case Anthony W., et al.
Title: Statistics and Polarization of Type III Radio Bursts Observed in the Inner Heliosphere
Abstract:

We present initial results from the Radio Frequency Spectrometer, the high-frequency component of the FIELDS experiment on the Parker Solar Probe (PSP). During the first PSP solar encounter (2018 November), only a few small radio bursts were observed. During the second encounter (2019 April), copious type III radio bursts occurred, including intervals of radio storms where bursts occurred continuously. In this paper, we present initial observations of the characteristics of type III radio bursts in the inner heliosphere, calculating occurrence rates, amplitude distributions, and spectral properties of the observed bursts. We also report observations of several bursts during the second encounter that display circular polarization in the right-hand-polarized sense, with a degree of polari. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 49 DOI: 10.3847/1538-4365/ab5dc0 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5dc0
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Authors: Pulupa Marc, Bale Stuart D., Badman Samuel T., Bonnell J. W., Case Anthony W., et al.
Title: Statistics and Polarization of Type III Radio Bursts Observed in the Inner Heliosphere
Abstract:

We present initial results from the Radio Frequency Spectrometer, the high-frequency component of the FIELDS experiment on the Parker Solar Probe (PSP). During the first PSP solar encounter (2018 November), only a few small radio bursts were observed. During the second encounter (2019 April), copious type III radio bursts occurred, including intervals of radio storms where bursts occurred continuously. In this paper, we present initial observations of the characteristics of type III radio bursts in the inner heliosphere, calculating occurrence rates, amplitude distributions, and spectral properties of the observed bursts. We also report observations of several bursts during the second encounter that display circular polarization in the right-hand-polarized sense, with a degree of polari. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 49 DOI: 10.3847/1538-4365/ab5dc0 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5dc0
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Authors: Lario D., Balmaceda L., Alzate N., Mays M. L., Richardson I. G., et al.
Title: The Streamer Blowout Origin of a Flux Rope and Energetic Particle Event Observed by Parker Solar Probe at 0.5 au
Abstract:

The distribution of spacecraft in the inner heliosphere during 2019 March enabled comprehensive observations of an interplanetary coronal mass ejection (ICME) that encountered Parker Solar Probe (PSP) at 0.547 au from the Sun. This ICME originated as a slow (∼311 km s-1) streamer blowout (SBO) on the Sun as measured by the white-light coronagraphs on board the Solar TErrestrial RElations Observatory-A and the Solar and Heliospheric Observatory. Despite its low initial speed, the passage of the ICME at PSP was preceded by an anisotropic, energetic (≲100 keV/n) ion enhancement and by two interplanetary shocks. The ICME was embedded between slow (∼300 km s-1) solar wind and a following, relatively high-speed (∼500 km s-1), stream that most likely wa. . .
Date: 07/2020 Publisher: The Astrophysical Journal Pages: 134 DOI: 10.3847/1538-4357/ab9942 Available at: https://iopscience.iop.org/article/10.3847/1538-4357/ab9942https://iopscience.iop.org/article/10.3847/1538-4357/ab9942/
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Authors: Lario D., Balmaceda L., Alzate N., Mays M. L., Richardson I. G., et al.
Title: The Streamer Blowout Origin of a Flux Rope and Energetic Particle Event Observed by Parker Solar Probe at 0.5 au
Abstract:

The distribution of spacecraft in the inner heliosphere during 2019 March enabled comprehensive observations of an interplanetary coronal mass ejection (ICME) that encountered Parker Solar Probe (PSP) at 0.547 au from the Sun. This ICME originated as a slow (\~311 km s-1) streamer blowout (SBO) on the Sun as measured by the white-light coronagraphs on board the Solar TErrestrial RElations Observatory-A and the Solar and Heliospheric Observatory. Despite its low initial speed, the passage of the ICME at PSP was preceded by an anisotropic, energetic (≲100 keV/n) ion enhancement and by two interplanetary shocks. The ICME was embedded between slow (\~300 km s-1) solar wind and a following, relatively high-speed (\~500 km s-1), stream that most likely was r. . .
Date: 07/2020 Publisher: The Astrophysical Journal Pages: 134 DOI: 10.3847/1538-4357/ab9942 Available at: https://iopscience.iop.org/article/10.3847/1538-4357/ab9942https://iopscience.iop.org/article/10.3847/1538-4357/ab9942/
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Authors: Agapitov O. V., de Wit Dudok, Mozer F. S., Bonnell J. W., Drake J. F., et al.
Title: Sunward-propagating Whistler Waves Collocated with Localized Magnetic Field Holes in the Solar Wind: Parker Solar Probe Observations at 35.7 R Radii
Abstract:

Observations by the Parker Solar Probe mission of the solar wind at \~35.7 solar radii reveal the existence of whistler wave packets with frequencies below 0.1 fce (20-80 Hz in the spacecraft frame). These waves often coincide with local minima of the magnetic field magnitude or with sudden deflections of the magnetic field that are called switchbacks. Their sunward propagation leads to a significant Doppler frequency downshift from 200-300 to 20-80 Hz (from 0.2 to 0.5 fce). The polarization of these waves varies from quasi-parallel to significantly oblique with wave normal angles that are close to the resonance cone. Their peak amplitude can be as large as 2-4 nT. Such values represent approximately 10% of the background magnetic field, which is considerably more . . .
Date: 03/2020 Publisher: The Astrophysical Journal Pages: L20 DOI: 10.3847/2041-8213/ab799c Available at: https://iopscience.iop.org/article/10.3847/2041-8213/ab799c
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Authors: Wiedenbeck M. E., Bučík R., Mason G. M., Ho G. C., Leske R. A., et al.
Title: 3 He-rich Solar Energetic Particle Observations at the Parker Solar Probe and near Earth
Abstract:

The Integrated Science Investigation of the Sun (IS☉IS) instrument suite on the Parker Solar Probe (PSP) spacecraft is making in situ observations of energetic ions and electrons closer to the Sun than any previous mission. Using data collected during its first two orbits, which reached perihelion distances of 0.17 au, we have searched for  3 He 3He -rich solar energetic particle (SEP) events under very quiet solar minimum conditions. On 2019-110-111 (April 20-21),  3 He 3He -rich SEPs were observed at energies near 1 MeV nucleon-1 in association with energetic protons, heavy ions, and electrons. This activity was also detected by the Ultra-Low-Energy Isotope Spectrometer and the Electron, Proton, and Alpha Monitor instruments on the Advanced C. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 42 DOI: 10.3847/1538-4365/ab5963 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5963
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Authors: de Wit Thierry Dudok, Krasnoselskikh Vladimir V., Bale Stuart D., Bonnell John W., Bowen Trevor A., et al.
Title: Switchbacks in the Near-Sun Magnetic Field: Long Memory and Impact on the Turbulence Cascade
Abstract:

One of the most striking observations made by Parker Solar Probe during its first solar encounter is the omnipresence of rapid polarity reversals in a magnetic field that is otherwise mostly radial. These so-called switchbacks strongly affect the dynamics of the magnetic field. We concentrate here on their macroscopic properties. First, we find that these structures are self-similar, and have neither a characteristic magnitude, nor a characteristic duration. Their waiting time statistics show evidence of aggregation. The associated long memory resides in their occurrence rate, and is not inherent to the background fluctuations. Interestingly, the spectral properties of inertial range turbulence differ inside and outside of switchback structures; in the latter the 1/f range extends to hi. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 39 DOI: 10.3847/1538-4365/ab5853 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5853
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Authors: Mozer F. S., Agapitov O. V., Bale S. D., Bonnell J. W., Case T., et al.
Title: Switchbacks in the Solar Magnetic Field: Their Evolution, Their Content, and Their Effects on the Plasma
Abstract:

Switchbacks (rotations of the magnetic field) are observed on the Parker Solar Probe. Their evolution, content, and plasma effects are studied in this paper. The solar wind does not receive a net acceleration from switchbacks that it encountered upstream of the observation point. The typical switchback rotation angle increased with radial distance. Significant Poynting fluxes existed inside, but not outside, switchbacks, and the dependence of the Poynting flux amplitude on the switchback radial location and rotation angle is explained quantitatively as being proportional to (B sin(θ))2. The solar wind flow inside switchbacks was faster than that outside due to the frozen-in ions moving with the magnetic structure at the Alfvén speed. This energy gain results from the diverg. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 68 DOI: 10.3847/1538-4365/ab7196 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab7196
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