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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: 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 eve. . .
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: Mozer F. S., and Hull A.
Title: Scaling the energy conversion rate from magnetic field reconnection to different bodies
Abstract:

Magnetic field reconnection is often invoked to explain electromagnetic energy conversion in planetary magnetospheres, stellar coronae, and other astrophysical objects. Because of the huge dynamic range of magnetic fields in these bodies, it is important to understand energy conversion as a function of magnetic field strength and related parameters. It is conjectured theoretically and shown experimentally that the energy conversion rate per unit area in reconnection scales as the cube of an appropriately weighted magnetic field strength divided by the square root of an appropriately weighted density. With this functional dependence, the energy release in flares on the Sun, the large and rapid variation of the magnetic flux in the tail of Mercury, and the apparent absence of reconnection. . .
Date: 10/2010 Publisher: Physics of Plasmas Pages: 102906 DOI: 10.1063/1.3504224 Available at: http://aip.scitation.org/doi/10.1063/1.3504224http://aip.scitation.org/doi/pdf/10.1063/1.3504224
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Authors: Mozer F. S., and Hull A.
Title: Scaling the energy conversion rate from magnetic field reconnection to different bodies
Abstract:

Magnetic field reconnection is often invoked to explain electromagnetic energy conversion in planetary magnetospheres, stellar coronae, and other astrophysical objects. Because of the huge dynamic range of magnetic fields in these bodies, it is important to understand energy conversion as a function of magnetic field strength and related parameters. It is conjectured theoretically and shown experimentally that the energy conversion rate per unit area in reconnection scales as the cube of an appropriately weighted magnetic field strength divided by the square root of an appropriately weighted density. With this functional dependence, the energy release in flares on the Sun, the large and rapid variation of the magnetic flux in the tail of Mercury, and the apparent absence of reconnection. . .
Date: 10/2010 Publisher: Physics of Plasmas Pages: 102906 DOI: 10.1063/1.3504224 Available at: http://aip.scitation.org/doi/10.1063/1.3504224http://aip.scitation.org/doi/pdf/10.1063/1.3504224
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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: 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: 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: 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: Mondal Surajit, Oberoi Divya, and Mohan Atul
Title: First Radio Evidence for Impulsive Heating Contribution to the Quiet Solar Corona
Abstract:

This Letter explores the relevance of nanoflare-based models for heating the quiet Sun corona. Using meterwave data from the Murchison Widefield Array, we present the first successful detection of impulsive emissions down to flux densities of ∼mSFU, about two orders of magnitude weaker than earlier attempts. These impulsive emissions have durations ≲1 s and are present throughout the quiet solar corona. The fractional time occupancy of these impulsive emissions at a given region is ≲10%. The histograms of these impulsive emissions follow a power-law distribution and show signs of clustering at small timescales. Our estimate of the energy that must be dumped in the corona to generate these impulsive emissions is consistent with the coronal heating requirements. Additionally, the st. . .
Date: 06/2020 Publisher: The Astrophysical Journal Pages: L39 DOI: 10.3847/2041-8213/ab8817 Available at: https://iopscience.iop.org/article/10.3847/2041-8213/ab8817https://iopscience.iop.org/article/10.3847/2041-8213/ab8817/
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Authors: Mondal Surajit, Oberoi Divya, and Mohan Atul
Title: First Radio Evidence for Impulsive Heating Contribution to the Quiet Solar Corona
Abstract:

This Letter explores the relevance of nanoflare-based models for heating the quiet Sun corona. Using meterwave data from the Murchison Widefield Array, we present the first successful detection of impulsive emissions down to flux densities of \~mSFU, about two orders of magnitude weaker than earlier attempts. These impulsive emissions have durations ≲1 s and are present throughout the quiet solar corona. The fractional time occupancy of these impulsive emissions at a given region is ≲10%. The histograms of these impulsive emissions follow a power-law distribution and show signs of clustering at small timescales. Our estimate of the energy that must be dumped in the corona to generate these impulsive emissions is consistent with the coronal heating requirements. Additionally, the sta. . .
Date: 06/2020 Publisher: The Astrophysical Journal Pages: L39 DOI: 10.3847/2041-8213/ab8817 Available at: https://iopscience.iop.org/article/10.3847/2041-8213/ab8817https://iopscience.iop.org/article/10.3847/2041-8213/ab8817/
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Authors: Moncuquet Michel, Meyer-Vernet Nicole, Issautier Karine, Pulupa Marc, Bonnell J. W., et al.
Title: First In Situ Measurements of Electron Density and Temperature from Quasi-thermal Noise Spectroscopy with Parker Solar Probe /FIELDS
Abstract:

Heat transport in the solar corona and wind is still a major unsolved astrophysical problem. Because of the key role played by electrons, the electron density and temperature(s) are important prerequisites for understanding these plasmas. We present such in situ measurements along the two first solar encounters of the Parker Solar Probe, between 0.5 and 0.17 au from the Sun, revealing different states of the emerging solar wind near the solar activity minimum. These preliminary results are obtained from a simplified analysis of the plasma quasi-thermal noise (QTN) spectrum measured by the Radio Frequency Spectrometer (FIELDS). The local electron density is deduced from the tracking of the plasma line, which enables accurate measurements, independent of calibrations and spacecraft pertur. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 44 DOI: 10.3847/1538-4365/ab5a84 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5a84
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Authors: Moncuquet Michel, Meyer-Vernet Nicole, Issautier Karine, Pulupa Marc, Bonnell J. W., et al.
Title: First In Situ Measurements of Electron Density and Temperature from Quasi-thermal Noise Spectroscopy with Parker Solar Probe /FIELDS
Abstract:

Heat transport in the solar corona and wind is still a major unsolved astrophysical problem. Because of the key role played by electrons, the electron density and temperature(s) are important prerequisites for understanding these plasmas. We present such in situ measurements along the two first solar encounters of the Parker Solar Probe, between 0.5 and 0.17 au from the Sun, revealing different states of the emerging solar wind near the solar activity minimum. These preliminary results are obtained from a simplified analysis of the plasma quasi-thermal noise (QTN) spectrum measured by the Radio Frequency Spectrometer (FIELDS). The local electron density is deduced from the tracking of the plasma line, which enables accurate measurements, independent of calibrations and spacecraft pertur. . .
Date: 02/2020 Publisher: The Astrophysical Journal Supplement Series Pages: 44 DOI: 10.3847/1538-4365/ab5a84 Available at: https://iopscience.iop.org/article/10.3847/1538-4365/ab5a84
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Authors: Milligan Ryan O., and Ireland Jack
Title: On the Performance of Multi-Instrument Solar Flare Observations During Solar Cycle 24
Abstract:

The current fleet of space-based solar observatories offers us a wealth of opportunities to study solar flares over a range of wavelengths. Significant advances in our understanding of flare physics often come from coordinated observations between multiple instruments. Consequently, considerable efforts have been, and continue to be, made to coordinate observations among instruments ( e.g. through the Max Millennium Program of Solar Flare Research). However, there has been no study to date that quantifies how many flares have been observed by combinations of various instruments. Here we describe a technique that retrospectively searches archival databases for flares jointly observed by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI), Solar Dynamics Observatory (SDO)/ EUV Vari. . .
Date: 02/2018 Publisher: Solar Physics DOI: 10.1007/s11207-017-1233-x Available at: http://link.springer.com/10.1007/s11207-017-1233-xhttp://link.springer.com/content/pdf/10.1007/s11207-017-1233-x.pdfhttp://link.springer.com/article/10.1007/s11207-017-1233-x/fulltext.htmlhttp://link.springer.com/content/pdf/10.1007/s11207-017-1233-x.pdf
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Authors: Milligan Ryan O., and Ireland Jack
Title: On the Performance of Multi-Instrument Solar Flare Observations During Solar Cycle 24
Abstract:

The current fleet of space-based solar observatories offers us a wealth of opportunities to study solar flares over a range of wavelengths. Significant advances in our understanding of flare physics often come from coordinated observations between multiple instruments. Consequently, considerable efforts have been, and continue to be, made to coordinate observations among instruments ( e.g. through the Max Millennium Program of Solar Flare Research). However, there has been no study to date that quantifies how many flares have been observed by combinations of various instruments. Here we describe a technique that retrospectively searches archival databases for flares jointly observed by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI), Solar Dynamics Observatory (SDO)/ EUV Vari. . .
Date: 02/2018 Publisher: Solar Physics DOI: 10.1007/s11207-017-1233-x Available at: http://link.springer.com/10.1007/s11207-017-1233-xhttp://link.springer.com/content/pdf/10.1007/s11207-017-1233-x.pdfhttp://link.springer.com/article/10.1007/s11207-017-1233-x/fulltext.htmlhttp://link.springer.com/content/pdf/10.1007/s11207-017-1233-x.pdf
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Authors: Meyer‐Vernet Nicole, and Moncuquet Michel
Title: Plasma Waves in Space: The Importance of Properly Accounting for the Measuring Device
Abstract:

Electric fields are generally measured or calculated using two intuitive assumptions: (1) the electric field equals the voltage divided by the antenna length when the antenna is electromagnetically short (2) the antenna responds best to electric field along its length. Both assumptions are often incorrect for electrostatic fields because they scale as the Debye length or as the electron gyroradius, which may be smaller than the antenna length. Taking into account this little-known fact enables us to complete or correct several recent papers on plasma spontaneous fluctuations in various solar system environments.


Date: 03/2020 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2019JA027723 Available at: https://onlinelibrary.wiley.com/doi/abs/10.1029/2019JA027723
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Authors: Meyer-Vernet Nicole, and Moncuquet Michel
Title: Plasma Waves in Space: The Importance of Properly Accounting for the Measuring Device
Abstract:

Electric fields are generally measured or calculated using two intuitive assumptions: (1) the electric field equals the voltage divided by the antenna length when the antenna is electromagnetically short (2) the antenna responds best to electric field along its length. Both assumptions are often incorrect for electrostatic fields because they scale as the Debye length or as the electron gyroradius, which may be smaller than the antenna length. Taking into account this little-known fact enables us to complete or correct several recent papers on plasma spontaneous fluctuations in various solar system environments.


Date: 03/2020 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2019JA027723 Available at: https://onlinelibrary.wiley.com/doi/abs/10.1029/2019JA027723
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Authors: Meyer-Vernet N., Issautier K., and Moncuquet M.
Title: Quasi-thermal noise spectroscopy: The art and the practice
Abstract:

Quasi-thermal noise spectroscopy is an efficient tool for measuring in situ macroscopic plasma properties in space, using a passive wave receiver at the ports of an electric antenna. This technique was pioneered on spinning spacecraft carrying very long dipole antennas in the interplanetary medium—like ISEE-3 and Ulysses—whose geometry approached a "theoretician's dream." The technique has been extended to other instruments in various types of plasmas on board different spacecraft and will be implemented on several missions in the near future. Such extensions require different theoretical modelizations, involving magnetized, drifting, or dusty plasmas with various particle velocity distributions and antennas being shorter, biased, or made of unequal wires. We give new analytical app. . .
Date: 08/2017 Publisher: Journal of Geophysical Research: Space Physics Pages: 7925 - 7945 DOI: 10.1002/2017JA024449 Available at: http://doi.wiley.com/10.1002/2017JA024449http://onlinelibrary.wiley.com/wol1/doi/10.1002/2017JA024449/fullpdf
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Authors: Meyer-Vernet N., Issautier K., and Moncuquet M.
Title: Quasi-thermal noise spectroscopy: The art and the practice
Abstract:

Quasi-thermal noise spectroscopy is an efficient tool for measuring in situ macroscopic plasma properties in space, using a passive wave receiver at the ports of an electric antenna. This technique was pioneered on spinning spacecraft carrying very long dipole antennas in the interplanetary medium—like ISEE-3 and Ulysses—whose geometry approached a "theoretician’s dream." The technique has been extended to other instruments in various types of plasmas on board different spacecraft and will be implemented on several missions in the near future. Such extensions require different theoretical modelizations, involving magnetized, drifting, or dusty plasmas with various particle velocity distributions and antennas being shorter, biased, or made of unequal wires. We give new analytical a. . .
Date: 08/2017 Publisher: Journal of Geophysical Research: Space Physics Pages: 7925 - 7945 DOI: 10.1002/2017JA024449 Available at: http://doi.wiley.com/10.1002/2017JA024449http://onlinelibrary.wiley.com/wol1/doi/10.1002/2017JA024449/fullpdf
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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. . .
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: 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: McComas D. J., Christian E. R., Cohen C. M. S., Cummings A. C., Davis A. J., et al.
Title: Probing the energetic particle environment near the Sun
Abstract:

NASA's Parker Solar Probe mission recently plunged through the inner heliosphere of the Sun to its perihelia, about 24 million kilometres from the Sun. Previous studies farther from the Sun (performed mostly at a distance of 1 astronomical unit) indicate that solar energetic particles are accelerated from a few kiloelectronvolts up to near-relativistic energies via at least two processes: "impulsive" events, which are usually associated with magnetic reconnection in solar flares and are typically enriched in electrons, helium-3 and heavier ions, and "gradual" events, which are typically associated with large coronal-mass-ejection-driven shocks and compressions moving through the corona and inner solar wind and are the dominant source of protons with energies between 1 and 10 megaelectro. . .
Date: 12/2019 Publisher: Nature Pages: 223 - 227 DOI: 10.1038/s41586-019-1811-1 Available at: http://www.nature.com/articles/s41586-019-1811-1
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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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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., Christian E. R., Cohen C. M. S., Cummings A. C., Davis A. J., et al.
Title: Probing the energetic particle environment near the Sun
Abstract:

NASA’s Parker Solar Probe mission recently plunged through the inner heliosphere of the Sun to its perihelia, about 24 million kilometres from the Sun. Previous studies farther from the Sun (performed mostly at a distance of 1 astronomical unit) indicate that solar energetic particles are accelerated from a few kiloelectronvolts up to near-relativistic energies via at least two processes: "impulsive" events, which are usually associated with magnetic reconnection in solar flares and are typically enriched in electrons, helium-3 and heavier ions, and "gradual" events, which are typically associated with large coronal-mass-ejection-driven shocks and compressions moving through the corona and inner solar wind and are the dominant source of protons with energies between 1 and 10 megaelect. . .
Date: 12/2019 Publisher: Nature Pages: 223 - 227 DOI: 10.1038/s41586-019-1811-1 Available at: http://www.nature.com/articles/s41586-019-1811-1
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Authors: Matthaeus H., Weygand M., and Dasso S.
Title: Ensemble Space-Time Correlation of Plasma Turbulence in the Solar Wind
Abstract:

Single point measurement turbulence cannot distinguish variations in space and time. We employ an ensemble of one- and two-point measurements in the solar wind to estimate the space-time correlation function in the comoving plasma frame. The method is illustrated using near Earth spacecraft observations, employing ACE, Geotail, IMP-8, and Wind data sets. New results include an evaluation of both correlation time and correlation length from a single method, and a new assessment of the accuracy of the familiar frozen-in flow approximation. This novel view of the space-time structure of turbulence may prove essential in exploratory space missions such as Solar Probe Plus and Solar Orbiter for which the frozen-in flow hypothesis may not be a useful approximation.


Date: 06/2016 Publisher: Physical Review Letters DOI: 10.1103/PhysRevLett.116.245101 Available at: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.245101
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