Found 12 results
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2020
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: 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: Szabo Adam, Larson Davin, Whittlesey Phyllis, Stevens Michael L., Lavraud Benoit, et al.
Title: The Heliospheric Current Sheet in the Inner Heliosphere Observed by the Parker Solar Probe
Abstract:

The Parker Solar Probe (PSP) completed its first solar encounter in 2018 November, bringing it closer to the Sun than any previous mission. This allowed in situ investigation of the heliospheric current sheet (HCS) inside the orbit of Venus. The Parker observations reveal a well defined magnetic sector structure placing the spacecraft in a negative polarity region for most of the encounter. The observed current sheet crossings are compared to the predictions of both potential field source surface and magnetohydrodynamic models. All the model predictions are in good qualitative agreement with the observed crossings of the HCS. The models also generally agree that the HCS was nearly parallel with the solar equator during the inbound leg of the encounter and more significantly inclined dur. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 47 DOI: 10.3847/1538-4365/ab5dac Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5dach
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Authors: Vech Daniel, Kasper Justin C., Klein Kristopher G., Huang Jia, Stevens Michael L., et al.
Title: Kinetic-scale Spectral Features of Cross Helicity and Residual Energy in the Inner Heliosphere
Abstract:

In this work, we present the first results from the flux angle (FA) operation mode of the Faraday Cup instrument on board the Parker Solar Probe (PSP). The FA mode allows rapid measurements of phase space density fluctuations close to the peak of the proton velocity distribution function with a cadence of 293 Hz. This approach provides an invaluable tool for understanding kinetic-scale turbulence in the solar wind and solar corona. We describe a technique to convert the phase space density fluctuations into vector velocity components and compute several turbulence parameters, such as spectral index, residual energy, and cross helicity during two intervals when the FA mode was used in PSP's first encounter at 0.174 au distance from the Sun.


Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 52 DOI: 10.3847/1538-4365/ab60a2 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab60a2
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Authors: Badman Samuel T., Bale Stuart D., Oliveros Juan C. Martín, Panasenco Olga, Velli Marco, et al.
Title: Magnetic Connectivity of the Ecliptic Plane within 0.5 au: Potential Field Source Surface Modeling of the First Parker Solar Probe Encounter
Abstract:

We compare magnetic field measurements taken by the FIELDS instrument on board Parker Solar Probe (PSP) during its first solar encounter to predictions obtained by potential field source surface (PFSS) modeling. Ballistic propagation is used to connect the spacecraft to the source surface. Despite the simplicity of the model, our results show striking agreement with PSP's first observations of the heliospheric magnetic field from ̃0.5 au (107.5 R) down to 0.16 au (35.7 R). Further, we show the robustness of the agreement is improved both by allowing the photospheric input to the model to vary in time, and by advecting the field from PSP down to the PFSS model domain using in situ PSP/Solar Wind Electrons Alphas and Protons measurements of the solar wind spee. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 23 DOI: 10.3847/1538-4365/ab4da7 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab4da7
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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: 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 o. . .
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: 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: 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: 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 . . .
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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2019
Authors: Wilson Lynn B., Chen Li-Jen, Wang Shan, Schwartz Steven J., Turner Drew L., et al.
Title: Electron Energy Partition across Interplanetary Shocks. II. Statistics
Abstract:

A statistical analysis of 15,210 electron velocity distribution function (VDF) fits, observed within ±2 hr of 52 interplanetary (IP) shocks by the Wind spacecraft near 1 au, is presented. This is the second in a three-part series on electron VDFs near IP shocks. The electron velocity moment statistics for the dense, low-energy core, tenuous, hot halo, and field-aligned beam/strahl are a statistically significant list of values illustrated with both histograms and tabular lists for reference and baselines in future work. Given the large statistics in this investigation, the beam/strahl fit results in the upstream are now the most comprehensive attempt to parameterize the beam/strahl electron velocity moments in the ambient solar wind. The median density, temperature, beta, and temperatu. . .
Date: 12/2019 Publisher: The Astrophysical Journal Supplement Series Pages: 24 DOI: 10.3847/1538-4365/ab5445 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5445
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2015
Authors: Kasper Justin C., Abiad Robert, Austin Gerry, Balat-Pichelin Marianne, Bale Stuart D., et al.
Title: Solar Wind Electrons Alphas and Protons (SWEAP) Investigation: Design of the Solar Wind and Coronal Plasma Instrument Suite for Solar Probe Plus
Abstract:

The Solar Wind Electrons Alphas and Protons (SWEAP) Investigation on Solar Probe Plus is a four sensor instrument suite that provides complete measurements of the electrons and ionized helium and hydrogen that constitute the bulk of solar wind and coronal plasma. SWEAP consists of the Solar Probe Cup (SPC) and the Solar Probe Analyzers (SPAN). SPC is a Faraday Cup that looks directly at the Sun and measures ion and electron fluxes and flow angles as a function of energy. SPAN consists of an ion and electron electrostatic analyzer (ESA) on the ram side of SPP (SPAN-A) and an electron ESA on the anti-ram side (SPAN-B). The SPAN-A ion ESA has a time of flight section that enables it to sort particles by their mass/charge ratio, permitting differentiation of ion species. SPAN-A and -B are r. . .
Date: 10/2015 Publisher: Space Science Reviews DOI: 10.1007/s11214-015-0206-3 Available at: http://link.springer.com/10.1007/s11214-015-0206-3http://link.springer.com/content/pdf/10.1007/s11214-015-0206-3
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