Found 209 results
Author Title Type [ Year(Desc)]
2020
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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Authors: Réville Victor, Velli Marco, Rouillard Alexis P., Lavraud Benoit, Tenerani Anna, et al.
Title: Tearing Instability and Periodic Density Perturbations in the Slow Solar Wind
Abstract:

In contrast with the fast solar wind, which originates in coronal holes, the source of the slow solar wind is still debated. Often intermittent and enriched with low first ionization potential elements—akin to what is observed in closed coronal loops—the slow wind could form in bursty events nearby helmet streamers. Slow winds also exhibit density perturbations that have been shown to be periodic and could be associated with flux ropes ejected from the tip of helmet streamers, as shown recently by the WISPR white-light imager on board Parker Solar Probe (PSP). In this work, we propose that the main mechanism controlling the release of flux ropes is a flow-modified tearing mode at the heliospheric current sheet (HCS). We use magnetohydrodynamic simulations of the solar wind and coron. . .
Date: 05/2020 Publisher: The Astrophysical Journal Pages: L20 DOI: 10.3847/2041-8213/ab911d Available at: https://iopscience.iop.org/article/10.3847/2041-8213/ab911d
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Authors: Mozer F. S., Agapitov O. V., Bale S. D., Bonnell J. W., Goetz K., et al.
Title: Time Domain Structures and Dust in the Solar Vicinity: Parker Solar Probe Observations
Abstract:

On 2019 April 5, while the Parker Solar Probe was at its 35 solar radius perihelion, the data set collected at 293 samples/s contained more than 10,000 examples of spiky electric-field-like structures with durations less than 200 milliseconds and amplitudes greater than 10 mV m-1. The vast majority of these events were caused by plasma turbulence. Defining dust events as those with similar, narrowly peaked, positive, and single-ended signatures resulted in finding 135 clear dust events, which, after correcting for the low detection efficiently, resulted in an estimate consistent with the 1000 dust events expected from other techniques. Defining time domain structures (TDS) as those with opposite polarity signals in the opposite antennas resulted in finding 238 clear TDS event. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 50 DOI: 10.3847/1538-4365/ab5e4b Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5e4b
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Authors: Adhikari L., Zank G. P., Zhao L.-L., Kasper J. C., Korreck K. E., et al.
Title: Turbulence Transport Modeling and First Orbit Parker Solar Probe ( PSP ) Observations
Abstract:

The Parker Solar Probe (PSP) achieved its first orbit perihelion on 2018 November 6, reaching a heliocentric distance of about 0.165 au (35.55 R). Here, we study the evolution of fully developed turbulence associated with the slow solar wind along the PSP trajectory between 35.55 R and 131.64 R in the outbound direction, comparing observations to a theoretical turbulence transport model. Several turbulent quantities, such as the fluctuating kinetic energy and the corresponding correlation length, the variance of density fluctuations, and the solar wind proton temperature are determined from the PSP Solar Wind Electrons Alphas and Protons (SWEAP) plasma data along its trajectory between 35.55 R and 131.64 R. The evolut. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 38 DOI: 10.3847/1538-4365/ab5852 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5852
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Authors: Longcope Dana
Title: Using Kepler’s laws and Rutherford scattering to chart the seven gravity assists in the epic sunward journey of the Parker Solar Probe
Abstract:

On August 12, 2018, NASA launched the Parker Solar Probe (PSP) to explore regions very near the Sun. Losing enough energy and angular momentum to approach the Sun requires either an impractical amount of fuel or a maneuver called a gravity assist. A gravity assist is essentially an elastic collision with a massive, moving target—Rutherford scattering from a planet. Gravity assists are often used to gain energy in missions destined for the outer solar system, but they can also be used to lose energy. Reaching an orbit sufficiently close to the Sun requires that PSP undergoes not one but seven successive gravity assists off the planet Venus. This simple description poses several conceptual challenges to the curious physics student. Why is it so much more challenging to get to the Sun th. . .
Date: 01/2020 Publisher: American Journal of Physics Pages: 11 - 19 DOI: 10.1119/10.0000145 Available at: http://aapt.scitation.org/doi/10.1119/10.0000145http://aapt.scitation.org/doi/pdf/10.1119/10.0000145
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Authors: Cheng Long, Zhang Quanhao, Wang Yuming, Li Xiaolei, and Liu Rui
Title: Using Stereoscopic Observations of Cometary Plasma Tails to Infer Solar Wind Speed
Abstract:

Detection of the solar wind speed near the Sun is significant in understanding the heating and acceleration of the solar wind. Cometary plasma tails have long been used as natural probes for solar wind speed; previous solar wind speed estimates via plasma tails, however, were based on comet images from a single viewpoint, and the projection effect may influence the result. Using stereoscopic observations from the Solar Terrestrial Relations Observatory and the Solar and Heliospheric Observatory, we three-dimensionally reconstruct the plasma tails of three comets C/2012 S1 (ISON), C/2010 E6, and C/2011 W3 (Lovejoy) and infer the ambient solar wind speed. The first comet is located between 3.5 and 6 solar radii (Rs) away from the Sun at high latitudes; the estimated solar wind speed is ab. . .
Date: 07/2020 Publisher: The Astrophysical Journal Pages: 87 DOI: 10.3847/1538-4357/ab93b6 Available at: https://iopscience.iop.org/article/10.3847/1538-4357/ab93b6https://iopscience.iop.org/article/10.3847/1538-4357/ab93b6/pdf
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Authors: Morgan Huw, and Cook Anthony C.
Title: The Width, Density, and Outflow of Solar Coronal Streamers
Abstract:

Characterizing the large-scale structure and plasma properties of the inner corona is crucial to understanding the source and subsequent expansion of the solar wind and related space weather effects. Here, we apply a new coronal rotational tomography method, along with a method to narrow streamers and refine the density estimate, to COR2A/Solar Terrestrial Relations Observatory observations from a period near solar minimum and maximum, gaining density maps for heights between 4 and 8R. The coronal structure is highly radial at these heights, and the streamers are very narrow: in some regions, only a few degrees in width. The mean densities of streamers is almost identical between solar minimum and maximum. However, streamers at solar maximum contain around 50% more total m. . .
Date: 04/2020 Publisher: The Astrophysical Journal Pages: 57 DOI: 10.3847/1538-4357/ab7e32 Available at: https://iopscience.iop.org/article/10.3847/1538-4357/ab7e32
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Authors: Hess Phillip, Rouillard Alexis P., Kouloumvakos Athanasios, Liewer Paulett C., Zhang Jie, et al.
Title: WISPR Imaging of a Pristine CME
Abstract:

The Wide-field Imager for Solar Probe (WISPR) on board the Parker Solar Probe (PSP) observed a coronal mass ejection (CME) on 2018 November 1, the first day of the initial PSP encounter. The speed of the CME, approximately 200-300 km s-1 in the WISPR field of view, is typical of slow, streamer blowout CMEs. This event was also observed by the Large Angle and Spectrometric Coronagraph Experiment (LASCO) coronagraphs. WISPR and LASCO view remarkably similar structures that enable useful cross-comparison between the two data sets as well as stereoscopic imaging of the CME. An analysis is extended to lower heights by linking the white-light observations to extreme ultraviolet (EUV) data from the Atmospheric Imaging Assembly, which reveal a structure that erupts more than a full d. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 25 DOI: 10.3847/1538-4365/ab4ff0 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab4ff0
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