Found 9 results
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Filters: Author is Maksimovic, M.  [Clear All Filters]
2020
Authors: Maksimovic M., Bale S. D., Berčič L., Bonnell J. W., Case A. W., et al.
Title: Anticorrelation between the Bulk Speed and the Electron Temperature in the Pristine Solar Wind: First Results from the Parker Solar Probe and Comparison with Helios
Abstract:

We discuss the solar wind electron temperatures Te as measured in the nascent solar wind by Parker Solar Probe during its first perihelion pass. The measurements have been obtained by fitting the high-frequency part of quasi-thermal noise spectra recorded by the Radio Frequency Spectrometer. In addition we compare these measurements with those obtained by the electrostatic analyzer discussed in Halekas et al. These first electron observations show an anticorrelation between Te and the wind bulk speed V: this anticorrelation is most likely the remnant of the well-known mapping observed at 1 au and beyond between the fast wind and its coronal hole sources, where electrons are observed to be cooler than in the quiet corona. We also revisit Helios electron temperature . . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 62 DOI: 10.3847/1538-4365/ab61fc Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab61fch
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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: Lavraud B., Fargette N., Réville V., Szabo A., Huang J., et al.
Title: The Heliospheric Current Sheet and Plasma Sheet during Parker Solar Probe’s First Orbit
Abstract:

We present heliospheric current sheet (HCS) and plasma sheet (HPS) observations during Parker Solar Probe’s (PSP) first orbit around the Sun. We focus on the eight intervals that display a true sector boundary (TSB; based on suprathermal electron pitch angle distributions) with one or several associated current sheets. The analysis shows that (1) the main density enhancements in the vicinity of the TSB and HCS are typically associated with electron strahl dropouts, implying magnetic disconnection from the Sun, (2) the density enhancements are just about twice that in the surrounding regions, suggesting mixing of plasmas from each side of the HCS, (3) the velocity changes at the main boundaries are either correlated or anticorrelated with magnetic field changes, consistent with magneti. . .
Date: 05/2020 Publisher: The Astrophysical Journal Pages: L19 DOI: 10.3847/2041-8213/ab8d2d Available at: https://iopscience.iop.org/article/10.3847/2041-8213/ab8d2d
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Authors: Velli M., Harra L. K., Vourlidas A., Schwadron N., Panasenco O., et al.
Title: Understanding the origins of the heliosphere: integrating observations and measurements from Parker Solar Probe, Solar Orbiter, and other space- and ground-based observatories
Abstract:

Context. The launch of Parker Solar Probe (PSP) in 2018, followed by Solar Orbiter (SO) in February 2020, has opened a new window in the exploration of solar magnetic activity and the origin of the heliosphere. These missions, together with other space observatories dedicated to solar observations, such as the Solar Dynamics Observatory, Hinode, IRIS, STEREO, and SOHO, with complementary in situ observations from WIND and ACE, and ground based multi-wavelength observations including the DKIST observatory that has just seen first light, promise to revolutionize our understanding of the solar atmosphere and of solar activity, from the generation and emergence of the Sun's magnetic field to the creation of the&. . .
Date: 09/2020 Publisher: Astronomy & Astrophysics Pages: A4 DOI: 10.1051/0004-6361/202038245 Available at: https://www.aanda.org/10.1051/0004-6361/202038245https://www.aanda.org/10.1051/0004-6361/202038245/pdf
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2019
Authors: Bale S. D., Badman S. T., Bonnell J. W., Bowen T. A., Burgess D., et al.
Title: Highly structured slow solar wind emerging from an equatorial coronal hole
Abstract:

During the solar minimum, when the Sun is at its least active, the solar wind is observed at high latitudes as a predominantly fast (more than 500 kilometres per second), highly Alfvénic rarefied stream of plasma originating from deep within coronal holes. Closer to the ecliptic plane, the solar wind is interspersed with a more variable slow wind of less than 500 kilometres per second. The precise origins of the slow wind streams are less certain; theories and observations suggest that they may originate at the tips of helmet streamers, from interchange reconnection near coronal hole boundaries, or within coronal holes with highly diverging magnetic fields. The heating mechanism required to drive the solar wind is also unresolved, although candidate mechanisms include Alfvé;n-wave tur. . .
Date: 12/2019 Publisher: Nature Pages: 237 - 242 DOI: 10.1038/s41586-019-1818-7 Available at: http://www.nature.com/articles/s41586-019-1818-7
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2017
Authors: Pulupa M., Bale S. D., Bonnell J. W., Bowen T. A., Carruth N., et al.
Title: The solar probe plus radio frequency spectrometer: Measurement requirements, analog design, and digital signal processing
Abstract:

The Radio Frequency Spectrometer (RFS) is a two-channel digital receiver and spectrometer, which will make remote sensing observations of radio waves and in situ measurements of electrostatic and electromagnetic fluctuations in the solar wind. A part of the FIELDS suite for Solar Probe Plus (SPP), the RFS is optimized for measurements in the inner heliosphere, where solar radio bursts are more intense and the plasma frequency is higher compared to previous measurements at distances of 1 AU or greater. The inputs to the RFS receiver are the four electric antennas mounted near the front of the SPP spacecraft and a single axis of the SPP search coil magnetometer (SCM). Each RFS channel selects a monopole or dipole antenna input, or the SCM input, via multiplexers. The primary data products. . .
Date: 03/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023345 Available at: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016JA023345
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Authors: Kasper J. C., Klein K. G., Weber T., Maksimovic M., Zaslavsky A., et al.
Title: A Zone of Preferential Ion Heating Extends Tens of Solar Radii from the Sun
Abstract:

The extreme temperatures and nonthermal nature of the solar corona and solar wind arise from an unidentified physical mechanism that preferentially heats certain ion species relative to others. Spectroscopic indicators of unequal temperatures commence within a fraction of a solar radius above the surface of the Sun, but the outer reach of this mechanism has yet to be determined. Here we present an empirical procedure for combining interplanetary solar wind measurements and a modeled energy equation including Coulomb relaxation to solve for the typical outer boundary of this zone of preferential heating. Applied to two decades of observations by the Wind spacecraft, our results are consistent with preferential heating being active in a zone extending from the transition region in the low. . .
Date: 11/2017 Publisher: The Astrophysical Journal Pages: 126 DOI: 10.3847/1538-4357/aa84b1 Available at: http://stacks.iop.org/0004-637X/849/i=2/a=126?key=crossref.a4fda357a12d19fd2ad1aa8a3897c78f
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2016
Authors: Bale S. D., Goetz K., Harvey P. R., Turin P., Bonnell J. W., et al.
Title: The FIELDS Instrument Suite for Solar Probe Plus
Abstract:

NASA’s Solar Probe Plus (SPP) mission will make the first in situ measurements of the solar corona and the birthplace of the solar wind. The FIELDS instrument suite on SPP will make direct measurements of electric and magnetic fields, the properties of in situ plasma waves, electron density and temperature profiles, and interplanetary radio emissions, amongst other things. Here, we describe the scientific objectives targeted by the SPP/FIELDS instrument, the instrument design itself, and the instrument concept of operations and planned data products.


Date: 12/2016 Publisher: Space Science Reviews Pages: 49 - 82 DOI: 10.1007/s11214-016-0244-5 Available at: http://link.springer.com/10.1007/s11214-016-0244-5http://link.springer.com/content/pdf/10.1007/s11214-016-0244-5.pd
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2010
Authors: Ergun R. E., Malaspina D. M., Bale S. D., McFadden J. P., Larson D. E., et al.
Title: Spacecraft charging and ion wake formation in the near-Sun environment
Abstract:

A three-dimensional, self-consistent code is employed to solve for the static potential structure surrounding a spacecraft in a high photoelectron environment. The numerical solutions show that, under certain conditions, a spacecraft can take on a negative potential in spite of strong photoelectron currents. The negative potential is due to an electrostatic barrier near the surface of the spacecraft that can reflect a large fraction of the photoelectron flux back to the spacecraft. This electrostatic barrier forms if (1) the photoelectron density at the surface of the spacecraft greatly exceeds the ambient plasma density, (2) the spacecraft size is significantly larger than local Debye length of the photoelectrons, and (3) the thermal electron energy is much larger than the characterist. . .
Date: 07/2010 Publisher: Physics of Plasmas Pages: 072903 DOI: 10.1063/1.3457484 Available at: http://aip.scitation.org/doi/10.1063/1.3457484http://aip.scitation.org/doi/pdf/10.1063/1.3457484
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