Found 126 results
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2020
Authors: Chhiber Rohit, Goldstein M L., Maruca B. A., Chasapis A., Matthaeus W. H., et al.
Title: Clustering of Intermittent Magnetic and Flow Structures near Parker Solar Probe ’s First Perihelion—A Partial-variance-of-increments Analysis
Abstract:

During the Parker Solar Probe’s (PSP) first perihelion pass, the spacecraft reached within a heliocentric distance of ̃37 R and observed numerous magnetic and flow structures characterized by sharp gradients. To better understand these intermittent structures in the young solar wind, an important property to examine is their degree of correlation in time and space. To this end, we use the well-tested partial variance of increments (PVI) technique to identify intermittent events in FIELDS and SWEAP observations of magnetic and proton-velocity fields (respectively) during PSP’s first solar encounter, when the spacecraft was within 0.25 au from the Sun. We then examine distributions of waiting times (WT) between events with varying separation and PVI thresholds. We find . . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 31 DOI: 10.3847/1538-4365/ab53d2 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab53d2
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Authors: Chhiber Rohit, Goldstein M L., Maruca B. A., Chasapis A., Matthaeus W. H., et al.
Title: Clustering of Intermittent Magnetic and Flow Structures near Parker Solar Probe ’s First Perihelion—A Partial-variance-of-increments Analysis
Abstract:

During the Parker Solar Probe's (PSP) first perihelion pass, the spacecraft reached within a heliocentric distance of ̃37 R and observed numerous magnetic and flow structures characterized by sharp gradients. To better understand these intermittent structures in the young solar wind, an important property to examine is their degree of correlation in time and space. To this end, we use the well-tested partial variance of increments (PVI) technique to identify intermittent events in FIELDS and SWEAP observations of magnetic and proton-velocity fields (respectively) during PSP's first solar encounter, when the spacecraft was within 0.25 au from the Sun. We then examine distributions of waiting times (WT) between events with varying separation and PVI thresholds. We find powe. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 31 DOI: 10.3847/1538-4365/ab53d2 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab53d2
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Authors: Bowen Trevor A., Mallet Alfred, Bale Stuart D., Bonnell J. W., Case Anthony W., et al.
Title: Constraining Ion-Scale Heating and Spectral Energy Transfer in Observations of Plasma Turbulence
Abstract:

We perform a statistical study of the turbulent power spectrum at inertial and kinetic scales observed during the first perihelion encounter of the Parker Solar Probe. We find that often there is an extremely steep scaling range of the power spectrum just above the ion-kinetic scales, similar to prior observations at 1 A.U., with a power-law index of around -4 . Based on our measurements, we demonstrate that either a significant (>50 %) fraction of the total turbulent energy flux is dissipated in this range of scales, or the characteristic nonlinear interaction time of the turbulence decreases dramatically from the expectation based solely on the dispersive nature of nonlinearly interacting kinetic Alfvén waves.


Date: 07/2020 Publisher: Physical Review Letters DOI: 10.1103/PhysRevLett.125.025102 Available at: https://link.aps.org/doi/10.1103/PhysRevLett.125.025102http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevLett.125.025102/fulltexthttps://link.aps.org/article/10.1103/PhysRevLett.125.025102
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Authors: Bowen Trevor A., Mallet Alfred, Bale Stuart D., Bonnell J. W., Case Anthony W., et al.
Title: Constraining Ion-Scale Heating and Spectral Energy Transfer in Observations of Plasma Turbulence
Abstract:

We perform a statistical study of the turbulent power spectrum at inertial and kinetic scales observed during the first perihelion encounter of the Parker Solar Probe. We find that often there is an extremely steep scaling range of the power spectrum just above the ion-kinetic scales, similar to prior observations at 1 A.U., with a power-law index of around -4 . Based on our measurements, we demonstrate that either a significant (>50 %) fraction of the total turbulent energy flux is dissipated in this range of scales, or the characteristic nonlinear interaction time of the turbulence decreases dramatically from the expectation based solely on the dispersive nature of nonlinearly interacting kinetic Alfvén waves.


Date: 07/2020 Publisher: Physical Review Letters DOI: 10.1103/PhysRevLett.125.025102 Available at: https://link.aps.org/doi/10.1103/PhysRevLett.125.025102http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevLett.125.025102/fulltexthttps://link.aps.org/article/10.1103/PhysRevLett.125.025102
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Authors: Berčič Laura, Larson Davin, Whittlesey Phyllis, Maksimovic Milan, Badman Samuel T., et al.
Title: Coronal Electron Temperature Inferred from the Strahl Electrons in the Inner Heliosphere: Parker Solar Probe and Helios Observations
Abstract:

The shape of the electron velocity distribution function plays an important role in the dynamics of the solar wind acceleration. Electrons are normally modeled with three components, the core, the halo, and the strahl. We investigate how well the fast strahl electrons in the inner heliosphere preserve the information about the coronal electron temperature at their origin. We analyzed the data obtained by two missions, Helios, spanning the distances between 65 and 215 RS, and Parker Solar Probe (PSP), reaching down to 35 RS during its first two orbits around the Sun. The electron strahl was characterized with two parameters: pitch-angle width (PAW) and the strahl parallel temperature (Ts||). PSP observations confirm the already reported dependence of stra. . .
Date: 04/2020 Publisher: The Astrophysical Journal Pages: 88 DOI: 10.3847/1538-4357/ab7b7a Available at: https://iopscience.iop.org/article/10.3847/1538-4357/ab7b7a
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Authors: Berčič Laura, Larson Davin, Whittlesey Phyllis, Maksimovic Milan, Badman Samuel T., et al.
Title: Coronal Electron Temperature Inferred from the Strahl Electrons in the Inner Heliosphere: Parker Solar Probe and Helios Observations
Abstract:

The shape of the electron velocity distribution function plays an important role in the dynamics of the solar wind acceleration. Electrons are normally modeled with three components, the core, the halo, and the strahl. We investigate how well the fast strahl electrons in the inner heliosphere preserve the information about the coronal electron temperature at their origin. We analyzed the data obtained by two missions, Helios, spanning the distances between 65 and 215 RS, and Parker Solar Probe (PSP), reaching down to 35 RS during its first two orbits around the Sun. The electron strahl was characterized with two parameters: pitch-angle width (PAW) and the strahl parallel temperature (Ts∥). PSP observations confirm the already reported dependence of str. . .
Date: 04/2020 Publisher: The Astrophysical Journal Pages: 88 DOI: 10.3847/1538-4357/ab7b7a Available at: https://iopscience.iop.org/article/10.3847/1538-4357/ab7b7a
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Authors: Sterling Alphonse C., and Moore Ronald L.
Title: Coronal-jet-producing Minifilament Eruptions as a Possible Source of Parker Solar Probe Switchbacks
Abstract:

The Parker Solar Probe (PSP) has observed copious rapid magnetic field direction changes in the near-Sun solar wind. These features have been called "switchbacks," and their origin is a mystery. But their widespread nature suggests that they may be generated by a frequently occurring process in the Sun's atmosphere. We examine the possibility that the switchbacks originate from coronal jets. Recent work suggests that many coronal jets result when photospheric magnetic flux cancels, and forms a small-scale "minifilament" flux rope that erupts and reconnects with coronal field. We argue that the reconnected erupting-minifilament flux rope can manifest as an outward propagating Alfvénic fluctuation that steepens into an increasingly compact disturbance as it moves through the solar wind. . . .
Date: 06/2020 Publisher: The Astrophysical Journal Pages: L18 DOI: 10.3847/2041-8213/ab96be Available at: https://iopscience.iop.org/article/10.3847/2041-8213/ab96behttps://iopscience.iop.org/article/10.3847/2041-8213/ab96be/
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Authors: Sterling Alphonse C., and Moore Ronald L.
Title: Coronal-jet-producing Minifilament Eruptions as a Possible Source of Parker Solar Probe Switchbacks
Abstract:

The Parker Solar Probe (PSP) has observed copious rapid magnetic field direction changes in the near-Sun solar wind. These features have been called "switchbacks," and their origin is a mystery. But their widespread nature suggests that they may be generated by a frequently occurring process in the Sun’s atmosphere. We examine the possibility that the switchbacks originate from coronal jets. Recent work suggests that many coronal jets result when photospheric magnetic flux cancels, and forms a small-scale "minifilament" flux rope that erupts and reconnects with coronal field. We argue that the reconnected erupting-minifilament flux rope can manifest as an outward propagating Alfvénic fluctuation that steepens into an increasingly compact disturbance as it moves through the solar wind. . .
Date: 06/2020 Publisher: The Astrophysical Journal Pages: L18 DOI: 10.3847/2041-8213/ab96be Available at: https://iopscience.iop.org/article/10.3847/2041-8213/ab96behttps://iopscience.iop.org/article/10.3847/2041-8213/ab96be/
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Authors: McManus Michael D., Bowen Trevor A., Mallet Alfred, Chen Christopher H. K., Chandran Benjamin D. G., et al.
Title: Cross Helicity Reversals in Magnetic Switchbacks
Abstract:

We consider 2D joint distributions of normalized residual energy, σr(s, t), and cross helicity, σc(s, t), during one day of Parker Solar Probe’s (PSP’s) first encounter as a function of wavelet scale s. The broad features of the distributions are similar to previous observations made by Helios in slow solar wind, namely well-correlated and fairly Alfvénic wind, except for a population with negative cross helicity that is seen at shorter wavelet scales. We show that this population is due to the presence of magnetic switchbacks, or brief periods where the magnetic field polarity reverses. Such switchbacks have been observed before, both in Helios data and in Ulysses data in the polar solar wind. Their abundance and short timescales as seen by PSP in its first. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 67 DOI: 10.3847/1538-4365/ab6dce Available at: https://iopscience.iop.org/article/10.3847/1538-4365
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Authors: McManus Michael D., Bowen Trevor A., Mallet Alfred, Chen Christopher H. K., Chandran Benjamin D. G., et al.
Title: Cross Helicity Reversals in Magnetic Switchbacks
Abstract:

We consider 2D joint distributions of normalized residual energy, σr(s, t), and cross helicity, σc(s, t), during one day of Parker Solar Probe's (PSP's) first encounter as a function of wavelet scale s. The broad features of the distributions are similar to previous observations made by Helios in slow solar wind, namely well-correlated and fairly Alfvénic wind, except for a population with negative cross helicity that is seen at shorter wavelet scales. We show that this population is due to the presence of magnetic switchbacks, or brief periods where the magnetic field polarity reverses. Such switchbacks have been observed before, both in Helios data and in Ulysses data in the polar solar wind. Their abundance and short timescales as seen by PSP in its first enc. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 67 DOI: 10.3847/1538-4365/ab6dce Available at: https://iopscience.iop.org/article/10.3847/1538-4365
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Authors: Krupar Vratislav, Szabo Adam, Maksimovic Milan, Kruparova Oksana, Kontar Eduard P., et al.
Title: Density Fluctuations in the Solar Wind Based on Type III Radio Bursts Observed by Parker Solar Probe
Abstract:

Radio waves are strongly scattered in the solar wind, so that their apparent sources seem to be considerably larger and shifted than the actual ones. Since the scattering depends on the spectrum of density turbulence, a better understanding of the radio wave propagation provides indirect information on the relative density fluctuations, ϵ=⟨δn⟩/⟨n⟩ ϵ=⟨δn⟩/⟨n⟩ , at the effective turbulence scale length. Here, we analyzed 30 type III bursts detected by Parker Solar Probe (PSP). For the first time, we retrieved type III burst decay times, τ d  τd , between 1 and 10 MHz thanks to an unparalleled temporal resolution of PSP. We observed a significant deviation in a power-law slope for frequencies above 1 MHz. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 57 DOI: 10.3847/1538-4365/ab65bd Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab65bd
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Authors: Krupar Vratislav, Szabo Adam, Maksimovic Milan, Kruparova Oksana, Kontar Eduard P., et al.
Title: Density Fluctuations in the Solar Wind Based on Type III Radio Bursts Observed by Parker Solar Probe
Abstract:

Radio waves are strongly scattered in the solar wind, so that their apparent sources seem to be considerably larger and shifted than the actual ones. Since the scattering depends on the spectrum of density turbulence, a better understanding of the radio wave propagation provides indirect information on the relative density fluctuations, ϵ=⟨δn⟩/⟨n⟩ ϵ=⟨δn⟩/⟨n⟩ , at the effective turbulence scale length. Here, we analyzed 30 type III bursts detected by Parker Solar Probe (PSP). For the first time, we retrieved type III burst decay times, τ d  τd , between 1 and 10 MHz thanks to an unparalleled temporal resolution of PSP. We observed a significant deviation in a power-law slope for frequencies above 1 MHz. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 57 DOI: 10.3847/1538-4365/ab65bd Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab65bd
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Authors: Poirier Nicolas, Kouloumvakos Athanasios, Rouillard Alexis P., Pinto Rui F., Vourlidas Angelos, et al.
Title: Detailed Imaging of Coronal Rays with the Parker Solar Probe
Abstract:

The Wide-field Imager for Solar PRobe (WISPR) obtained the first high-resolution images of coronal rays at heights below 15 R when the Parker Solar Probe (PSP) was located inside 0.25 au during the first encounter. We exploit these remarkable images to reveal the structure of coronal rays at scales that are not easily discernible in images taken from near 1 au. To analyze and interpret WISPR observations, which evolve rapidly both radially and longitudinally, we construct a latitude versus time map using the full WISPR data set from the first encounter. From the exploitation of this map and also from sequential WISPR images. we show the presence of multiple substructures inside streamers and pseudostreamers. WISPR unveils the fine-scale structure of the densest part of str. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 60 DOI: 10.3847/1538-4365/ab6324 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab6324
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Authors: Poirier Nicolas, Kouloumvakos Athanasios, Rouillard Alexis P., Pinto Rui F., Vourlidas Angelos, et al.
Title: Detailed Imaging of Coronal Rays with the Parker Solar Probe
Abstract:

The Wide-field Imager for Solar PRobe (WISPR) obtained the first high-resolution images of coronal rays at heights below 15 R when the Parker Solar Probe (PSP) was located inside 0.25 au during the first encounter. We exploit these remarkable images to reveal the structure of coronal rays at scales that are not easily discernible in images taken from near 1 au. To analyze and interpret WISPR observations, which evolve rapidly both radially and longitudinally, we construct a latitude versus time map using the full WISPR data set from the first encounter. From the exploitation of this map and also from sequential WISPR images. we show the presence of multiple substructures inside streamers and pseudostreamers. WISPR unveils the fine-scale structure of the densest part of str. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 60 DOI: 10.3847/1538-4365/ab6324 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab6324
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Authors: Chen Yu, and Hu Qiang
Title: Effects of Radial Distances on Small-scale Magnetic Flux Ropes in the Solar Wind
Abstract:

Small-scale magnetic flux ropes (SFRs) in the solar wind have been studied for decades. Statistical analysis utilizing various in situ spacecraft measurements is the main observational approach to investigating the generation and evolution of these small-scale structures. Based on the Grad-Shafranov reconstruction technique, we use the automated detection algorithm to build the databases of these small-scale structures via various spacecraft measurements at different heliocentric distances. We present the SFR properties, including the magnetic field and plasma parameters at different radial distances from the Sun near the ecliptic plane. It is found that the event occurrence rate is still of the order of a few hundreds per month, the duration and scale-size distributions follow power la. . .
Date: 05/2020 Publisher: The Astrophysical Journal Pages: 25 DOI: 10.3847/1538-4357/ab8294 Available at: https://iopscience.iop.org/article/10.3847/1538-4357/ab8294
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Authors: Chen Yu, and Hu Qiang
Title: Effects of Radial Distances on Small-scale Magnetic Flux Ropes in the Solar Wind
Abstract:

Small-scale magnetic flux ropes (SFRs) in the solar wind have been studied for decades. Statistical analysis utilizing various in situ spacecraft measurements is the main observational approach to investigating the generation and evolution of these small-scale structures. Based on the Grad-Shafranov reconstruction technique, we use the automated detection algorithm to build the databases of these small-scale structures via various spacecraft measurements at different heliocentric distances. We present the SFR properties, including the magnetic field and plasma parameters at different radial distances from the Sun near the ecliptic plane. It is found that the event occurrence rate is still of the order of a few hundreds per month, the duration and scale-size distributions follow power la. . .
Date: 05/2020 Publisher: The Astrophysical Journal Pages: 25 DOI: 10.3847/1538-4357/ab8294 Available at: https://iopscience.iop.org/article/10.3847/1538-4357/ab8294
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Authors: Halekas J. S., Whittlesey P., Larson D. E., McGinnis D., Maksimovic M., et al.
Title: Electrons in the Young Solar Wind: First Results from the Parker Solar Probe
Abstract:

The Solar Wind Electrons Alphas and Protons experiment on the Parker Solar Probe (PSP) mission measures the three-dimensional electron velocity distribution function. We derive the parameters of the core, halo, and strahl populations utilizing a combination of fitting to model distributions and numerical integration for ̃100,000 electron distributions measured near the Sun on the first two PSP orbits, which reached heliocentric distances as small as ̃0.17 au. As expected, the electron core density and temperature increase with decreasing heliocentric distance, while the ratio of electron thermal pressure to magnetic pressure (βe) decreases. These quantities have radial scaling consistent with previous observations farther from the Sun, with superposed variations associated. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 22 DOI: 10.3847/1538-4365/ab4cec Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab4cec
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Authors: Halekas J. S., Whittlesey P., Larson D. E., McGinnis D., Maksimovic M., et al.
Title: Electrons in the Young Solar Wind: First Results from the Parker Solar Probe
Abstract:

The Solar Wind Electrons Alphas and Protons experiment on the Parker Solar Probe (PSP) mission measures the three-dimensional electron velocity distribution function. We derive the parameters of the core, halo, and strahl populations utilizing a combination of fitting to model distributions and numerical integration for ̃100,000 electron distributions measured near the Sun on the first two PSP orbits, which reached heliocentric distances as small as ̃0.17 au. As expected, the electron core density and temperature increase with decreasing heliocentric distance, while the ratio of electron thermal pressure to magnetic pressure (βe) decreases. These quantities have radial scaling consistent with previous observations farther from the Sun, with superposed variations associated. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 22 DOI: 10.3847/1538-4365/ab4cec Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab4cec
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Authors: Cohen C. M. S., Christian E. R., Cummings A. C., Davis A. J., Desai M. I., et al.
Title: Energetic Particle Increases Associated with Stream Interaction Regions
Abstract:

The Parker Solar Probe was launched on 2018 August 12 and completed its second orbit on 2019 June 19 with perihelion of 35.7 solar radii. During this time, the Energetic Particle Instrument-Hi (EPI-Hi, one of the two energetic particle instruments comprising the Integrated Science Investigation of the Sun, IS☉IS) measured seven proton intensity increases associated with stream interaction regions (SIRs), two of which appear to be occurring in the same region corotating with the Sun. The events are relatively weak, with observed proton spectra extending to only a few MeV and lasting for a few days. The proton spectra are best characterized by power laws with indices ranging from −4.3 to −6.5, generally softer than events associated with SIRs observed at 1 au and beyond. Helium spec. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 20 DOI: 10.3847/1538-4365/ab4c38 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab4c38
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Authors: Cohen C. M. S., Christian E. R., Cummings A. C., Davis A. J., Desai M. I., et al.
Title: Energetic Particle Increases Associated with Stream Interaction Regions
Abstract:

The Parker Solar Probe was launched on 2018 August 12 and completed its second orbit on 2019 June 19 with perihelion of 35.7 solar radii. During this time, the Energetic Particle Instrument-Hi (EPI-Hi, one of the two energetic particle instruments comprising the Integrated Science Investigation of the Sun, IS☉IS) measured seven proton intensity increases associated with stream interaction regions (SIRs), two of which appear to be occurring in the same region corotating with the Sun. The events are relatively weak, with observed proton spectra extending to only a few MeV and lasting for a few days. The proton spectra are best characterized by power laws with indices ranging from -4.3 to -6.5, generally softer than events associated with SIRs observed at 1 au and beyond. Helium spectra . . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 20 DOI: 10.3847/1538-4365/ab4c38 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab4c38
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Authors: Joyce C. J., McComas D. J., Christian E. R., Schwadron N. A., Wiedenbeck M. E., et al.
Title: Energetic Particle Observations from the Parker Solar Probe Using Combined Energy Spectra from the IS⊙IS Instrument Suite
Abstract:

The Integrated Science Investigations of the Sun (IS☉IS) instrument suite includes two Energetic Particle instruments: EPI-Hi, designed to measure ions from ̃1 to 200 MeV nuc-1, and EPI-Lo, designed to measure ions from ̃20 to ̃15 MeV nuc-1. We present an analysis of eight energetic proton events observed across the energy range of both instruments during Parker Solar Probe’s (PSP) first two orbits in order to examine their combined energy spectra. Background corrections are applied to help resolve spectral breaks between the two instruments and are shown to be effective. In doing so we demonstrate that even in the early stages of calibration, IS☉IS is capable of producing reliable spectral observations across broad energy ranges. In addition to making gro. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 41 DOI: 10.3847/1538-4365/ab5948 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5948
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Authors: Joyce C. J., McComas D. J., Christian E. R., Schwadron N. A., Wiedenbeck M. E., et al.
Title: Energetic Particle Observations from the Parker Solar Probe Using Combined Energy Spectra from the IS⊙IS Instrument Suite
Abstract:

The Integrated Science Investigations of the Sun (IS☉IS) instrument suite includes two Energetic Particle instruments: EPI-Hi, designed to measure ions from ̃1 to 200 MeV nuc−1, and EPI-Lo, designed to measure ions from ̃20 to ̃15 MeV nuc−1. We present an analysis of eight energetic proton events observed across the energy range of both instruments during Parker Solar Probe's (PSP) first two orbits in order to examine their combined energy spectra. Background corrections are applied to help resolve spectral breaks between the two instruments and are shown to be effective. In doing so we demonstrate that even in the early stages of calibration, IS☉IS is capable of producing reliable spectral observations across broad energy ranges. In addition to making g. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 41 DOI: 10.3847/1538-4365/ab5948 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5948
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Authors: Bandyopadhyay Riddhi, Goldstein M. L., Maruca B. A., Matthaeus W. H., Parashar T. N., et al.
Title: Enhanced Energy Transfer Rate in Solar Wind Turbulence Observed near the Sun from Parker Solar Probe
Abstract:

Direct evidence of an inertial-range turbulent energy cascade has been provided by spacecraft observations in heliospheric plasmas. In the solar wind, the average value of the derived heating rate near 1 au is \~10 3 Jkg -1 s -1  \~103Jkg-1s-1 , an amount sufficient to account for observed departures from adiabatic expansion. Parker Solar Probe, even during its first solar encounter, offers the first opportunity to compute, in a similar fashion, a fluid-scale energy decay rate, much closer to the solar corona than any prior in situ observations. Using the Politano-Pouquet third-order law and the von Kármán decay law, we estimate the fluid-range energy transfer rate in the inner heliosphere, at heliocentric distance R ranging from 54 R (. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 48 DOI: 10.3847/1538-4365/ab5dae Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5dae
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Authors: Bandyopadhyay Riddhi, Goldstein M. L., Maruca B. A., Matthaeus W. H., Parashar T. N., et al.
Title: Enhanced Energy Transfer Rate in Solar Wind Turbulence Observed near the Sun from Parker Solar Probe
Abstract:

Direct evidence of an inertial-range turbulent energy cascade has been provided by spacecraft observations in heliospheric plasmas. In the solar wind, the average value of the derived heating rate near 1 au is ∼10 3 Jkg −1 s −1  ∼103Jkg−1s−1 , an amount sufficient to account for observed departures from adiabatic expansion. Parker Solar Probe, even during its first solar encounter, offers the first opportunity to compute, in a similar fashion, a fluid-scale energy decay rate, much closer to the solar corona than any prior in situ observations. Using the Politano─Pouquet third-order law and the von Kármán decay law, we estimate the fluid-range energy transfer rate in the inner heliosphere, at heliocentric distance R ranging from 54 RDate: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 48 DOI: 10.3847/1538-4365/ab5dae Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5dae
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Authors: Chen C. H. K., Bale S. D., Bonnell J. W., Borovikov D., Bowen T. A., et al.
Title: The Evolution and Role of Solar Wind Turbulence in the Inner Heliosphere
Abstract:

The first two orbits of the Parker Solar Probe spacecraft have enabled the first in situ measurements of the solar wind down to a heliocentric distance of 0.17 au (or 36 R ⊙  R⊙ ). Here, we present an analysis of this data to study solar wind turbulence at 0.17 au and its evolution out to 1 au. While many features remain similar, key differences at 0.17 au include increased turbulence energy levels by more than an order of magnitude, a magnetic field spectral index of −3/2 matching that of the velocity and both Elsasser fields, a lower magnetic compressibility consistent with a smaller slow-mode kinetic energy fraction, and a much smaller outer scale that has had time for substantial nonlinear processing. There is also an overall increase in the dominance o. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 53 DOI: 10.3847/1538-4365/ab60a3 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab60a3
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