Found 22 results
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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: 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: 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: 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: 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: Phan T. D., Bale S. D., Eastwood J. P., Lavraud B., Drake J. F., et al.
Title: Parker Solar Probe In Situ Observations of Magnetic Reconnection Exhausts during Encounter 1
Abstract:

Magnetic reconnection in current sheets converts magnetic energy into particle energy. The process may play an important role in the acceleration and heating of the solar wind close to the Sun. Observations from Parker Solar Probe (PSP) provide a new opportunity to study this problem, as it measures the solar wind at unprecedented close distances to the Sun. During the first orbit, PSP encountered a large number of current sheets in the solar wind through perihelion at 35.7 solar radii. We performed a comprehensive survey of these current sheets and found evidence for 21 reconnection exhausts. These exhausts were observed in heliospheric current sheets, coronal mass ejections, and regular solar wind. However, we find that the majority of current sheets encountered around perihelion, whe. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 34 DOI: 10.3847/1538-4365/ab55ee Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab55ee
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Authors: Phan T. D., Bale S. D., Eastwood J. P., Lavraud B., Drake J. F., et al.
Title: Parker Solar Probe In Situ Observations of Magnetic Reconnection Exhausts during Encounter 1
Abstract:

Magnetic reconnection in current sheets converts magnetic energy into particle energy. The process may play an important role in the acceleration and heating of the solar wind close to the Sun. Observations from Parker Solar Probe (PSP) provide a new opportunity to study this problem, as it measures the solar wind at unprecedented close distances to the Sun. During the first orbit, PSP encountered a large number of current sheets in the solar wind through perihelion at 35.7 solar radii. We performed a comprehensive survey of these current sheets and found evidence for 21 reconnection exhausts. These exhausts were observed in heliospheric current sheets, coronal mass ejections, and regular solar wind. However, we find that the majority of current sheets encountered around perihelion, whe. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 34 DOI: 10.3847/1538-4365/ab55ee Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab55ee
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Authors: Krasnoselskikh V., Larosa A., Agapitov O., de Wit Dudok, Moncuquet M., et al.
Title: Localized Magnetic-field Structures and Their Boundaries in the Near-Sun Solar Wind from Parker Solar Probe Measurements
Abstract:

One of the discoveries of the Parker Solar Probe during its first encounters with the Sun is ubiquitous presence of relatively small-scale structures standing out as sudden deflections of the magnetic field. They were named "switchbacks" since some of them show a full reversal of the radial component of the magnetic field and then return to "regular" conditions. We carried out an analysis of three typical switchback structures having different characteristics: I. Alfvénic structure, where the variations of the magnetic field components take place while conserving the magnitude of the magnetic field; II. Compressional structure, where the magnitude of the field varies together with changes of its components; and III. Structure manifesting full reversal of the magnetic field, presumably . . .
Date: 04/2020 Publisher: The Astrophysical Journal Pages: 93 DOI: 10.3847/1538-4357/ab7f2d Available at: https://iopscience.iop.org/article/10.3847/1538-4357/ab7f2d
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Authors: Krasnoselskikh V., Larosa A., Agapitov O., de Wit Dudok, Moncuquet M., et al.
Title: Localized Magnetic-field Structures and Their Boundaries in the Near-Sun Solar Wind from Parker Solar Probe Measurements
Abstract:

One of the discoveries of the Parker Solar Probe during its first encounters with the Sun is ubiquitous presence of relatively small-scale structures standing out as sudden deflections of the magnetic field. They were named "switchbacks" since some of them show a full reversal of the radial component of the magnetic field and then return to "regular" conditions. We carried out an analysis of three typical switchback structures having different characteristics: I. Alfvénic structure, where the variations of the magnetic field components take place while conserving the magnitude of the magnetic field; II. Compressional structure, where the magnitude of the field varies together with changes of its components; and III. Structure manifesting full reversal of the magnetic field, presumably . . .
Date: 04/2020 Publisher: The Astrophysical Journal Pages: 93 DOI: 10.3847/1538-4357/ab7f2d Available at: https://iopscience.iop.org/article/10.3847/1538-4357/ab7f2d
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Authors: Parashar T. N., Goldstein M. L., Maruca B. A., Matthaeus W. H., Ruffolo D., et al.
Title: Measures of Scale-dependent Alfvénicity in the First PSP Solar Encounter
Abstract:

The solar wind shows periods of highly Alfvénic activity, where velocity fluctuations and magnetic fluctuations are aligned or antialigned with each other. It is generally agreed that solar wind plasma velocity and magnetic field fluctuations observed by the Parker Solar Probe (PSP) during the first encounter are mostly highly Alfvénic. However, quantitative measures of Alfvénicity are needed to understand how the characterization of these fluctuations compares with standard measures from prior missions in the inner and outer heliosphere, in fast wind and slow wind, and at high and low latitudes. To investigate this issue, we employ several measures to quantify the extent of Alfvénicity—the Alfvén ratio rA, the normalized cross helicity σc, the normalized r. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 58 DOI: 10.3847/1538-4365/ab64e6 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab64e6
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Authors: Parashar T. N., Goldstein M. L., Maruca B. A., Matthaeus W. H., Ruffolo D., et al.
Title: Measures of Scale-dependent Alfvénicity in the First PSP Solar Encounter
Abstract:

The solar wind shows periods of highly Alfvénic activity, where velocity fluctuations and magnetic fluctuations are aligned or antialigned with each other. It is generally agreed that solar wind plasma velocity and magnetic field fluctuations observed by the Parker Solar Probe (PSP) during the first encounter are mostly highly Alfvénic. However, quantitative measures of Alfvénicity are needed to understand how the characterization of these fluctuations compares with standard measures from prior missions in the inner and outer heliosphere, in fast wind and slow wind, and at high and low latitudes. To investigate this issue, we employ several measures to quantify the extent of Alfvénicity—the Alfvén ratio rA, the normalized cross helicity σc, the normalized r. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 58 DOI: 10.3847/1538-4365/ab64e6 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab64e6
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Authors: Bandyopadhyay Riddhi, Matthaeus W. H., Parashar T. N., Chhiber R., Ruffolo D., et al.
Title: Observations of Energetic-particle Population Enhancements along Intermittent Structures near the Sun from the Parker Solar Probe
Abstract:

Observations at 1 au have confirmed that enhancements in measured energetic-particle (EP) fluxes are statistically associated with "rough" magnetic fields, i.e., fields with atypically large spatial derivatives or increments, as measured by the Partial Variance of Increments (PVI) method. One way to interpret this observation is as an association of the EPs with trapping or channeling within magnetic flux tubes, possibly near their boundaries. However, it remains unclear whether this association is a transport or local effect; i.e., the particles might have been energized at a distant location, perhaps by shocks or reconnection, or they might experience local energization or re-acceleration. The Parker Solar Probe (PSP), even in its first two orbits, offers a unique opportunity to study. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 61 DOI: 10.3847/1538-4365/ab6220 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab6220
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Authors: Bandyopadhyay Riddhi, Matthaeus W. H., Parashar T. N., Chhiber R., Ruffolo D., et al.
Title: Observations of Energetic-particle Population Enhancements along Intermittent Structures near the Sun from the Parker Solar Probe
Abstract:

Observations at 1 au have confirmed that enhancements in measured energetic-particle (EP) fluxes are statistically associated with "rough" magnetic fields, i.e., fields with atypically large spatial derivatives or increments, as measured by the Partial Variance of Increments (PVI) method. One way to interpret this observation is as an association of the EPs with trapping or channeling within magnetic flux tubes, possibly near their boundaries. However, it remains unclear whether this association is a transport or local effect; i.e., the particles might have been energized at a distant location, perhaps by shocks or reconnection, or they might experience local energization or re-acceleration. The Parker Solar Probe (PSP), even in its first two orbits, offers a unique opportunity to study. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 61 DOI: 10.3847/1538-4365/ab6220 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab6220
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Authors: Qudsi R. A., Maruca B. A., Matthaeus W. H., Parashar T. N., Bandyopadhyay Riddhi, et al.
Title: Observations of Heating along Intermittent Structures in the Inner Heliosphere from PSP Data
Abstract:

The solar wind proton temperature at 1 au has been found to be correlated with small-scale intermittent magnetic structures, i.e., regions with enhanced temperature are associated with coherent structures, such as current sheets. Using Parker Solar Probe data from the first encounter, we study this association using measurements of the radial proton temperature, employing the partial variance of increments (PVI) technique to identify intermittent magnetic structures. We observe that the probability density functions of high PVI events have higher median temperatures than those with lower PVI. The regions in space where PVI peaks were also locations that had enhanced temperatures when compared with similar regions, suggesting a heating mechanism in the young solar wind that is associated. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 46 DOI: 10.3847/1538-4365/ab5c19 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5c19
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Authors: Qudsi R. A., Maruca B. A., Matthaeus W. H., Parashar T. N., Bandyopadhyay Riddhi, et al.
Title: Observations of Heating along Intermittent Structures in the Inner Heliosphere from PSP Data
Abstract:

The solar wind proton temperature at 1 au has been found to be correlated with small-scale intermittent magnetic structures, i.e., regions with enhanced temperature are associated with coherent structures, such as current sheets. Using Parker Solar Probe data from the first encounter, we study this association using measurements of the radial proton temperature, employing the partial variance of increments (PVI) technique to identify intermittent magnetic structures. We observe that the probability density functions of high PVI events have higher median temperatures than those with lower PVI. The regions in space where PVI peaks were also locations that had enhanced temperatures when compared with similar regions, suggesting a heating mechanism in the young solar wind that is associated. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 46 DOI: 10.3847/1538-4365/ab5c19 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5c19
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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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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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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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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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2014
Authors: McComas D. J., Alexander N., Angold N., Bale S., Beebe C., et al.
Title: Integrated Science Investigation of the Sun (ISIS): Design of the Energetic Particle Investigation
Abstract:

The Integrated Science Investigation of the Sun (ISIS) is a complete science investigation on the Solar Probe Plus (SPP) mission, which flies to within nine solar radii of the Sun’s surface. ISIS comprises a two-instrument suite to measure energetic particles over a very broad energy range, as well as coordinated management, science operations, data processing, and scientific analysis. Together, ISIS observations allow us to explore the mechanisms of energetic particles dynamics, including their: (1) Origins—defining the seed populations and physical conditions necessary for energetic particle acceleration; (2) Acceleration—determining the roles of shocks, reconnection, waves, and turbulence in accelerating energetic particles; and (3) Transport—revealing how ener. . .
Date: 07/2014 Publisher: Space Science Reviews DOI: 10.1007/s11214-014-0059-1 Available at: http://link.springer.com/content/pdf/10.1007/s11214-014-0059-1
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Authors: McComas D. J., Alexander N., Angold N., Bale S., Beebe C., et al.
Title: Integrated Science Investigation of the Sun (ISIS): Design of the Energetic Particle Investigation
Abstract:

The Integrated Science Investigation of the Sun (ISIS) is a complete science investigation on the Solar Probe Plus (SPP) mission, which flies to within nine solar radii of the Sun’s surface. ISIS comprises a two-instrument suite to measure energetic particles over a very broad energy range, as well as coordinated management, science operations, data processing, and scientific analysis. Together, ISIS observations allow us to explore the mechanisms of energetic particles dynamics, including their: (1) Origins—defining the seed populations and physical conditions necessary for energetic particle acceleration; (2) Acceleration—determining the roles of shocks, reconnection, waves, and turbulence in accelerating energetic particles; and (3) Transport—revealing how ener. . .
Date: 07/2014 Publisher: Space Science Reviews DOI: 10.1007/s11214-014-0059-1 Available at: http://link.springer.com/content/pdf/10.1007/s11214-014-0059-1
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