Found 9 results
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2020
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: Martinović Mihailo M., Klein Kristopher G., Kasper Justin C., Case Anthony W., Korreck Kelly E., et al.
Title: The Enhancement of Proton Stochastic Heating in the Near-Sun Solar Wind
Abstract:

Stochastic heating (SH) is a nonlinear heating mechanism driven by the violation of magnetic moment invariance due to large-amplitude turbulent fluctuations producing diffusion of ions toward higher kinetic energies in the direction perpendicular to the magnetic field. It is frequently invoked as a mechanism responsible for the heating of ions in the solar wind. Here, we quantify for the first time the proton SH rate Q at radial distances from the Sun as close as 0.16 au, using measurements from the first two Parker Solar Probe encounters. Our results for both the amplitude and radial trend of the heating rate, Q ∝ r−2.5, agree with previous results based on the Helios data set at heliocentric distances from 0.3 to 0.9 au. Also in agreement wit. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 30 DOI: 10.3847/1538-4365/ab527f Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab527f
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Authors: Panasenco Olga, Velli Marco, D’Amicis Raffaella, Shi Chen, Réville Victor, et al.
Title: Exploring Solar Wind Origins and Connecting Plasma Flows from the Parker Solar Probe to 1 au: Nonspherical Source Surface and Alfvénic Fluctuations
Abstract:

The magnetic field measurements of the FIELDS instrument on the Parker Solar Probe (PSP) have shown intensities, throughout its first solar encounter, that require a very low source surface (SS) height ( R SS ⩽1.8R ⊙  RSS⩽1.8R⊙ ) to be reconciled with magnetic field measurements at the Sun via potential field extrapolation (PFSS). However, during PSP's second encounter, the situation went back to a more classic SS height ( R SS ⩽2.5R ⊙  RSS⩽2.5R⊙ ). Here we use high-resolution observations of the photospheric magnetic field (Solar Dynamics Observatory/Helioseismic and Magnetic Imager) to calculate neutral lines and boundaries of the open field regions for SS heights from 1.2 to 2.5 RDate: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 54 DOI: 10.3847/1538-4365/ab61f4 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab61f4
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Authors: Bowen Trevor A., Mallet Alfred, Huang Jia, Klein Kristopher G., Malaspina David M., et al.
Title: Ion-scale Electromagnetic Waves in the Inner Heliosphere
Abstract:

Understanding the physical processes in the solar wind and corona that actively contribute to heating, acceleration, and dissipation is a primary objective of NASA's Parker Solar Probe (PSP) mission. Observations of circularly polarized electromagnetic waves at ion scales suggest that cyclotron resonance and wave─particle interactions are dynamically relevant in the inner heliosphere. A wavelet-based statistical study of circularly polarized events in the first perihelion encounter of PSP demonstrates that transverse electromagnetic waves at ion resonant scales are observed in 30─50% of radial field intervals. Average wave amplitudes of approximately 4 nT are measured, while the mean duration of wave events is on the order of 20 s; however, long-duration wave events can exist withou. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 66 DOI: 10.3847/1538-4365/ab6c65 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/
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Authors: Tenerani Anna, Velli Marco, Matteini Lorenzo, Réville Victor, Shi Chen, et al.
Title: Magnetic Field Kinks and Folds in the Solar Wind
Abstract:

Parker Solar Probe (PSP) observations during its first encounter at 35.7 R have shown the presence of magnetic field lines that are strongly perturbed to the point that they produce local inversions of the radial magnetic field, known as switchbacks. Their counterparts in the solar wind velocity field are local enhancements in the radial speed, or jets, displaying (in all components) the velocity─magnetic field correlation typical of large amplitude Alfvén waves propagating away from the Sun. Switchbacks and radial jets have previously been observed over a wide range of heliocentric distances by Helios, Wind, and Ulysses, although they were prevalent in significantly faster streams than seen at PSP. Here we study via numerical magnetohydrodynamics simulations the evolut. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 32 DOI: 10.3847/1538-4365/ab53e1 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab53e1
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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 plasma wh. . .
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: 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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2014
Authors: Peck Alison B., Benn Chris R., Seaman Robert L., Korreck Kelly E., Kasper Justin C., et al.
Title: SPIE ProceedingsSolar Wind Electrons Alphas and Protons (SWEAP) Science Operations Center initial design and implementation
Abstract:

Solar Probe Plus, scheduled to launch in 2018, is a NASA mission that will fly through the Sun's atmosphere for the first time. It will employ a combination of in situ plasma measurements and remote sensing imaging to achieve the mission's primary goal: to understand how the Sun's corona is heated and how the solar wind is accelerated. The Solar Wind Electrons Alphas and Protons (SWEAP) instrument suite consists of a Faraday cup and three electrostatic analyzers. In order to accomplish the science objectives, an encounter-based operations scheme is needed. This paper will outline the SWEAP science operations center design and schemes for data selection and down link. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted f. . .
Date: Publisher: SPIE DOI: 10.1117/12.2057314 Available at: http://proceedings.spiedigitallibrary.org/proceeding.aspx?doi=10.1117/12.2057314
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