bluuebunny/crossref_metadata_2025 huggingface dataset:
Relating Streamer Flows to Density and Magnetic Structures at the Parker Solar Probe
Authors: Rouillard Alexis P. , Kouloumvakos Athanasios , Vourlidas Angelos , Kasper Justin , Bale Stuart , Raouafi Nour-Edine , Lavraud Benoit , Howard Russell A. , Stenborg Guillermo , Stevens Michael , Poirier Nicolas , Davies Jackie A. , Hess Phillip , Higginson Aleida K. , Lavarra Michael , Viall Nicholeen M. , Korreck Kelly , Pinto Rui F. , Griton Léa , Réville Victor , Louarn Philippe , Wu Yihong , Dalmasse Kévin , Génot Vincent , Case Anthony W. , Whittlesey Phyllis , Larson Davin , Halekas Jasper S. , Livi Roberto , Goetz Keith , Harvey Peter R. , MacDowall Robert J. , Malaspina D. , Pulupa M. , Bonnell J. , de Witt T. Dudok , Penou Emmanuel
Published: February 2020

The physical mechanisms that produce the slow solar wind are still highly debated. Parker Solar Probe’s (PSP’s) second solar encounter provided a new opportunity to relate in situ measurements of the nascent slow solar wind with white-light images of streamer flows. We exploit data taken by the Solar and Heliospheric Observatory, the Solar TErrestrial RElations Observatory (STEREO), and the Wide Imager on Solar Probe to reveal for the first time a close link between imaged streamer flows and the high-density plasma measured by the Solar Wind Electrons Alphas and Protons (SWEAP) experiment. We identify different types of slow winds measured by PSP that we relate to the spacecraft’s magnetic connectivity (or not) to streamer flows. SWEAP measured high-density and highly variable plasma when PSP was well connected to streamers but more tenuous wind with much weaker density variations when it exited streamer flows. STEREO imaging of the release and propagation of small transients from the Sun to PSP reveals that the spacecraft was continually impacted by the southern edge of streamer transients. The impact of specific density structures is marked by a higher occurrence of magnetic field reversals measured by the FIELDS magnetometers. Magnetic reversals are associated with much stronger density variations inside than outside streamer flows. We tentatively interpret these findings in terms of magnetic reconnection between open magnetic fields and coronal loops with different properties, providing support for the formation of a subset of the slow wind by magnetic reconnection.
Predicting the Solar Wind at the Parker Solar Probe Using an Empirically Driven MHD Model
Authors: Kim T. K. , Pogorelov N. V. , Arge C. N. , Henney C. J. , Jones-Mecholsky S. I. , Smith W. P. , Bale S. D. , Bonnell J. W. , Dudok de Wit T. , Goetz K. , Harvey P. R. , MacDowall R. J. , Malaspina D. M. , Pulupa M. , Kasper J. C. , Korreck K. E. , Stevens M. , Case A. W. , Whittlesey P. , Livi R. , Larson D. E. , Klein K. G. , Zank G. P.
Published: February 2020

Since its launch on 2018 August 12, Parker Solar Probe (PSP) has completed its first and second orbits around the Sun, having reached down to 35.7 solar radii at each perihelion. In anticipation of the exciting new data at such unprecedented distances, we have simulated the global 3D heliosphere using an MHD model coupled with a semi-empirical coronal model using the best available photospheric magnetograms as input. We compare our heliospheric MHD simulation results with in situ measurements along the PSP trajectory from its launch to the completion of the second orbit, with particular emphasis on the solar wind structure around the first two solar encounters. Furthermore, we show our model prediction for the third perihelion, which occurred on 2019 September 1. Comparison of the MHD results with PSP observations provides new insights into solar wind acceleration. Moreover, PSP observations reveal how accurately the Air Force Data Assimilative Photospheric flux Transport-Wang-Sheeley-Arge-based predictions work throughout the inner heliosphere.
Energetic Particle Observations from the Parker Solar Probe Using Combined Energy Spectra from the IS⊙IS Instrument Suite
Authors: Joyce C. J. , McComas D. J. , Christian E. R. , Schwadron N. A. , Wiedenbeck M. E. , McNutt R. L. , Cohen C. M. S. , Leske R. A. , Mewaldt R. A. , Stone E. C. , Labrador A. W. , Davis A. J. , Cummings A. C. , Mitchell D. G. , Hill M. E. , Roelof E. C. , Szalay J. R. , Rankin J. S. , Desai M. I. , Giacalone J. , Matthaeus W. H.
Published: February 2020

The Integrated Science Investigations of the Sun (IS⊙IS) instrument suite includes two Energetic Particle instruments: EPI-Hi, designed to measure ions from ∼1 to 200 MeV nuc−1, and EPI-Lo, designed to measure ions from ∼20 to ∼15 MeV nuc−1. We present an analysis of eight energetic proton events observed across the energy range of both instruments during Parker Solar Probe’s (PSP) first two orbits in order to examine their combined energy spectra. Background corrections are applied to help resolve spectral breaks between the two instruments and are shown to be effective. In doing so we demonstrate that even in the early stages of calibration, IS⊙IS is capable of producing reliable spectral observations across broad energy ranges. In addition to making groundbreaking measurements very near the Sun, IS⊙IS also characterizes energetic particle populations over a range of heliocentric distances inside 1 au. During the first two orbits, IS⊙IS observed energetic particle events from a single corotating interaction region (CIR) at three different distances from the Sun. The events are separated by two Carrington rotations and just 0.11 au in distance; however, the relationship shown between proton intensities and proximity of the spacecraft to the source region shows evidence of the importance of transport effects on observations of energetic particles from CIRs. Future IS⊙IS observations of similar events over larger distances will help disentangle the effects of CIR-related acceleration and transport. We apply similar spectral analyses to the remaining five events, including four that are likely related to stream interaction regions (SIRs) and one solar energetic particle (SEP) event.
3He-rich Solar Energetic Particle Observations at the Parker Solar Probe and near Earth
Authors: Wiedenbeck M. E. , Bučík R. , Mason G. M. , Ho G. C. , Leske R. A. , Cohen C. M. S. , Christian E. R. , Cummings A. C. , Davis A. J. , Desai M. I. , Giacalone J. , Haggerty D. K. , Hill M. E. , Joyce C. J. , Labrador A. W. , Malandraki O. , Matthaeus W. H. , McComas D. J. , McNutt R. L. , Mewaldt R. A. , Mitchell D. G. , Posner A. , Rankin J. S. , Roelof E. C. , Schwadron N. A. , Stone E. C. , Szalay J. R. , Bale S. D. , Case A. W. , Kasper J. C. , Korreck K. E. , Larson D. E. , MacDowall R. J. , Pulupa M. , Stevens M. L.
Published: February 2020

The Integrated Science Investigation of the Sun (IS⊙IS) instrument suite on the Parker Solar Probe (PSP) spacecraft is making in situ observations of energetic ions and electrons closer to the Sun than any previous mission. Using data collected during its first two orbits, which reached perihelion distances of 0.17 au, we have searched for

-rich solar energetic particle (SEP) events under very quiet solar minimum conditions. On 2019-110–111 (April 20–21),

-rich SEPs were observed at energies near 1 MeV nucleon–1 in association with energetic protons, heavy ions, and electrons. This activity was also detected by the Ultra-Low-Energy Isotope Spectrometer and the Electron, Proton, and Alpha Monitor instruments on the Advanced Composition Explorer (ACE) spacecraft located near Earth, 0.99 au from the Sun. At that time, PSP and ACE were both magnetically connected to locations near the west limb of the Sun. Remote sensing measurements showed the presence of type III radio bursts and also helical jets from this region of the Sun. This combination of observations is commonly associated with

-rich SEP acceleration on the Sun. AR 12738, which was located at Carrington coordinates from which numerous X-ray flares were observed over a period of more than 6 months, was identified as the source of the

-rich events. This region was also the source of several other SEP events detected at PSP or ACE. Aside from the period in 2019 April, IS⊙IS did not observe any other

-rich SEPs during orbits 1 and 2.
First In Situ Measurements of Electron Density and Temperature from Quasi-thermal Noise Spectroscopy with Parker Solar Probe/FIELDS
Authors: Moncuquet Michel , Meyer-Vernet Nicole , Issautier Karine , Pulupa Marc , Bonnell J. W. , Bale Stuart D. , de Wit Thierry Dudok , Goetz Keith , Griton Léa , Harvey Peter R. , MacDowall Robert J. , Maksimovic Milan , Malaspina David M.
Published: February 2020

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 perturbations, whereas the temperatures of the thermal and suprathermal components of the velocity distribution, as well as the average kinetic temperature, are deduced from the shape of the plasma line. The temperature of the weakly collisional thermal population, similar for both encounters, decreases with the distance as R
−0.74, which is much slower than adiabatic. In contrast, the temperature of the nearly collisionless suprathermal population exhibits a virtually flat radial variation. The 7 s resolution of the density measurements enables us to deduce the low-frequency spectrum of compressive fluctuations around perihelion, varying as f
−1.4. This is the first time that QTN spectroscopy is implemented with an electric antenna length not exceeding the plasma Debye length. As PSP will approach the Sun, the decrease in the Debye length is expected to considerably improve the accuracy of the temperature measurements.
Sharp Alfvénic Impulses in the Near-Sun Solar Wind
Authors: Horbury Timothy S. , Woolley Thomas , Laker Ronan , Matteini Lorenzo , Eastwood Jonathan , Bale Stuart D. , Velli Marco , Chandran Benjamin D. G. , Phan Tai , Raouafi Nour E. , Goetz Keith , Harvey Peter R. , Pulupa Marc , Klein K. G. , Dudok de Wit Thierry , Kasper Justin C. , Korreck Kelly E. , Case A. W. , Stevens Michael L. , Whittlesey Phyllis , Larson Davin , MacDowall Robert J. , Malaspina David M. , Livi Roberto
Published: February 2020

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, due to the rather low Alfvén speeds in the streams observed by the spacecraft to date, these are still associated with large angular deflections of the magnetic field—and these deflections are not isotropic. These deflections do not appear to be related to the recently reported large-scale, pro-rotation solar wind flow. Estimates of the size and shape of the spikes reveal high aspect ratio flow-aligned structures with a transverse scale of ≈104 km. These events might be signatures of near-Sun impulsive reconnection events.
Observations of Heating along Intermittent Structures in the Inner Heliosphere from PSP Data
Authors: Qudsi R. A. , Maruca B. A. , Matthaeus W. H. , Parashar T. N. , Bandyopadhyay Riddhi , Chhiber R. , Chasapis A. , Goldstein Melvyn L. , Bale S. D. , Bonnell J. W. , Dudok de Wit T. , Goetz K. , Harvey P. R. , MacDowall R. J. , Malaspina D. , Pulupa M. , Kasper J. C. , Korreck K. E. , Case A. W. , Stevens M. , Whittlesey P. , Larson D. , Livi R. , Velli M. , Raouafi N.
Published: February 2020

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 with intermittency developed by a nonlinear turbulent cascade in the immediate vicinity.
Statistics and Polarization of Type III Radio Bursts Observed in the Inner Heliosphere
Authors: Pulupa Marc , Bale Stuart D. , Badman Samuel T. , Bonnell J. W. , Case Anthony W. , de Wit Thierry Dudok , Goetz Keith , Harvey Peter R. , Hegedus Alexander M. , Kasper Justin C. , Korreck Kelly E. , Krasnoselskikh Vladimir , Larson Davin , Lecacheux Alain , Livi Roberto , MacDowall Robert J. , Maksimovic Milan , Malaspina David M. , Martínez Oliveros Juan Carlos , Meyer-Vernet Nicole , Moncuquet Michel , Stevens Michael , Whittlesey Phyllis
Published: February 2020

We present initial results from the Radio Frequency Spectrometer, the high-frequency component of the FIELDS experiment on the Parker Solar Probe (PSP). During the first PSP solar encounter (2018 November), only a few small radio bursts were observed. During the second encounter (2019 April), copious type III radio bursts occurred, including intervals of radio storms where bursts occurred continuously. In this paper, we present initial observations of the characteristics of type III radio bursts in the inner heliosphere, calculating occurrence rates, amplitude distributions, and spectral properties of the observed bursts. We also report observations of several bursts during the second encounter that display circular polarization in the right-hand-polarized sense, with a degree of polarization of 0.15–0.38 in the range from 8 to 12 MHz. The degree of polarization can be explained either by depolarization of initially 100% polarized o-mode emission or by direct generation of emission in the o-mode and x-mode simultaneously. Direct in situ observations in future PSP encounters could provide data that can distinguish these mechanisms.
Time Domain Structures and Dust in the Solar Vicinity: Parker Solar Probe Observations
Authors: Mozer F. S. , Agapitov O. V. , Bale S. D. , Bonnell J. W. , Goetz K. , Goodrich K. A. , Gore R. , Harvey P. R. , Kellogg P. J. , Malaspina D. , Pulupa M. , Schumm G.
Published: February 2020

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 events which, after correcting for the detection efficiency, resulted in an estimated 500–1000 TDS events on this day. The TDS electric fields were bipolar, as expected for electron holes. Several events were found at times when the magnetic field was in the plane of the two measured components of the electric field such that the component of the electric field parallel to the magnetic field was measured. One example of significant parallel electric fields shows the negative potential that classified them as electron holes. Because the TDS observation rate was not uniform with time, it is likely that there were local regions below the spacecraft with field-aligned currents that generated the TDS.
Examining Dust Directionality with the Parker Solar Probe FIELDS Instrument
Authors: Page Brent , Bale Stuart D. , Bonnell J. W. , Goetz Keith , Goodrich Katherine , Harvey Peter R. , Larsen Rhiannon , MacDowall Robert J. , Malaspina David M. , Pokorný Petr , Pulupa Marc , Szalay Jamey R.
Published: February 2020

Parker Solar Probe’s (PSP’s) FIELDS instrument provides a measure of the dust impact rate on the spacecraft with a full-coverage summary of the voltages recorded by the spacecraft’s antennas. From consecutively sampled periods throughout PSP’s orbit, FIELDS stores the maximum amplitude measured by each active antenna. The occurrence of a dust impact during a given period can be identified by these amplitudes exceeding a few tens of millivolts, and a dust grain’s impact location can be approximated using the differential amplitudes between antennas. The impact locations indicated in the data are inspected for compatibility with the incident directions of prograde, retrograde, and β-meteoroid orbits in the ecliptic. Important features in the data are consistent with the incidence of β-meteoroids, but others are better explained by the incidence of grains on prograde or retrograde orbits.
Kinetic-scale Spectral Features of Cross Helicity and Residual Energy in the Inner Heliosphere
Authors: Vech Daniel , Kasper Justin C. , Klein Kristopher G. , Huang Jia , Stevens Michael L. , Chen Christopher H. K. , Case Anthony W. , Korreck Kelly , Bale Stuart D. , Bowen Trevor A. , Whittlesey Phyllis L. , Livi Roberto , Larson Davin E. , Malaspina David , Pulupa Marc , Bonnell John , Harvey Peter , Goetz Keith , Dudok de Wit Thierry , MacDowall Robert
Published: February 2020

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.
The Evolution and Role of Solar Wind Turbulence in the Inner Heliosphere
Authors: Chen C. H. K. , Bale S. D. , Bonnell J. W. , Borovikov D. , Bowen T. A. , Burgess D. , Case A. W. , Chandran B. D. G. , de Wit T. Dudok , Goetz K. , Harvey P. R. , Kasper J. C. , Klein K. G. , Korreck K. E. , Larson D. , Livi R. , MacDowall R. J. , Malaspina D. M. , Mallet A. , McManus M. D. , Moncuquet M. , Pulupa M. , Stevens M. L. , Whittlesey P.
Published: February 2020

The first two orbits of the Parker Solar Probe spacecraft have enabled the first in situ measurements of the solar wind down to a heliocentric distance of 0.17 au (or 36

). Here, we present an analysis of this data to study solar wind turbulence at 0.17 au and its evolution out to 1 au. While many features remain similar, key differences at 0.17 au include increased turbulence energy levels by more than an order of magnitude, a magnetic field spectral index of −3/2 matching that of the velocity and both Elsasser fields, a lower magnetic compressibility consistent with a smaller slow-mode kinetic energy fraction, and a much smaller outer scale that has had time for substantial nonlinear processing. There is also an overall increase in the dominance of outward-propagating Alfvénic fluctuations compared to inward-propagating ones, and the radial variation of the inward component is consistent with its generation by reflection from the large-scale gradient in Alfvén speed. The energy flux in this turbulence at 0.17 au was found to be ∼10% of that in the bulk solar wind kinetic energy, becoming ∼40% when extrapolated to the Alfvén point, and both the fraction and rate of increase of this flux toward the Sun are consistent with turbulence-driven models in which the solar wind is powered by this flux.
Exploring Solar Wind Origins and Connecting Plasma Flows from the Parker Solar Probe to 1 au: Nonspherical Source Surface and Alfvénic Fluctuations
Authors: Panasenco Olga , Velli Marco , D’Amicis Raffaella , Shi Chen , Réville Victor , Bale Stuart D. , Badman Samuel T. , Kasper Justin , Korreck Kelly , Bonnell J. W. , Wit Thierry Dudok de , Goetz Keith , Harvey Peter R. , MacDowall Robert J. , Malaspina David M. , Pulupa Marc , Case Anthony W. , Larson Davin , Livi Roberto , Stevens Michael , Whittlesey Phyllis
Published: February 2020

The magnetic field measurements of the FIELDS instrument on the Parker Solar Probe (PSP) have shown intensities, throughout its first solar encounter, that require a very low source surface (SS) height (

) to be reconciled with magnetic field measurements at the Sun via potential field extrapolation (PFSS). However, during PSP’s second encounter, the situation went back to a more classic SS height (

). Here we use high-resolution observations of the photospheric magnetic field (Solar Dynamics Observatory/Helioseismic and Magnetic Imager) to calculate neutral lines and boundaries of the open field regions for SS heights from 1.2 to 2.5 R
⊙ using an evolving PFSS model and the measured solar wind speed to trace the source of the wind observed by PSP to the low corona and photosphere. We adjust R
SS to get the best match for the field polarity over the period 2018 October–November and 2019 March–April, finding that the best fit for the observed magnetic field polarity inversions requires a nonspherical SS. The geometry of the coronal hole boundaries for different R
SS is tested using the PSP perihelion passes, 3D PFSS models, and LASCO/C2 observations. We investigate the sources of stronger-than-average magnetic fields and times of Alfvénic fast and slow wind. Only some of the strongly Alfvénic slow wind streams seen by PSP survive and are observed at 1 au: the origins and peculiar topology of the background in which they propagate is discussed.
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
Authors: Maksimovic M. , Bale S. D. , Berčič L. , Bonnell J. W. , Case A. W. , Wit T. Dudok de , Goetz K. , Halekas J. S. , Harvey P. R. , Issautier K. , Kasper J. C. , Korreck K. E. , Jagarlamudi V. Krishna , Lahmiti N. , Larson D. E. , Lecacheux A. , Livi R. , MacDowall R. J. , Malaspina D. M. , Martinović M. M. , Meyer-Vernet N. , Moncuquet M. , Pulupa M. , Salem C. , Stevens M. L. , Štverák Š. , Velli M. , Whittlesey P. L.
Published: February 2020

We discuss the solar wind electron temperatures T

e
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 T

e
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 measurements and show, for the first time, that an in situ (

) anticorrelation is well observed at 0.3 au but disappears as the wind expands, evolves, and mixes with different electron temperature gradients for different wind speeds.
Detailed Imaging of Coronal Rays with the Parker Solar Probe
Authors: Poirier Nicolas , Kouloumvakos Athanasios , Rouillard Alexis P. , Pinto Rui F. , Vourlidas Angelos , Stenborg Guillermo , Valette Emeline , Howard Russell A. , Hess Phillip , Thernisien Arnaud , Rich Nathan , Griton Lea , Indurain Mikel , Raouafi Nour-Edine , Lavarra Michael , Réville Victor
Published: February 2020

The Wide-field Imager for Solar PRobe (WISPR) obtained the first high-resolution images of coronal rays at heights below 15 R
⊙ when the Parker Solar Probe (PSP) was located inside 0.25 au during the first encounter. We exploit these remarkable images to reveal the structure of coronal rays at scales that are not easily discernible in images taken from near 1 au. To analyze and interpret WISPR observations, which evolve rapidly both radially and longitudinally, we construct a latitude versus time map using the full WISPR data set from the first encounter. From the exploitation of this map and also from sequential WISPR images. we show the presence of multiple substructures inside streamers and pseudostreamers. WISPR unveils the fine-scale structure of the densest part of streamer rays that we identify as the solar origin of the heliospheric plasma sheet typically measured in situ in the solar wind. We exploit 3D magnetohydrodynamic models, and we construct synthetic white-light images to study the origin of the coronal structures observed by WISPR. Overall, including the effect of the spacecraft relative motion toward the individual coronal structures, we can interpret several observed features by WISPR. Moreover, we relate some coronal rays to folds in the heliospheric current sheet that are unresolved from 1 au. Other rays appear to form as a result of the inherently inhomogeneous distribution of open magnetic flux tubes.
CME-associated Energetic Ions at 0.23 au: Consideration of the Auroral Pressure Cooker Mechanism Operating in the Low Corona as a Possible Energization Process
Authors: Mitchell D. G. , Giacalone J. , Allen R. C. , Hill M. E. , McNutt R. L. , McComas D. J. , Szalay J. R. , Schwadron N. A. , Rouillard A. P. , Bale S. B. , Chaston C. C. , Pulupa M. P. , Whittlesey P. L. , Kasper J. C. , MacDowall R. J. , Christian E. R. , Wiedenbeck M. E. , Matthaeus W. H.
Published: February 2020

We draw a comparison between a solar energetic particle event associated with the release of a slow coronal mass ejection close to the Sun, and the energetic particle population produced in high current density field-aligned current structures associated with auroral phenomena in planetary magnetospheres. We suggest that this process is common in CME development and lift off in the corona, and may account for the electron populations that generate Type III radio bursts, as well as for the prompt energetic ion and electron populations typically observed in interplanetary space.
Properties of Suprathermal-through-energetic He Ions Associated with Stream Interaction Regions Observed over the Parker Solar Probe’s First Two Orbits
Authors: Desai M. I. , Mitchell D. G. , Szalay J. R. , Roelof E. C. , Giacalone J. , Hill M. E. , McComas D. J. , Christian E. R. , Schwadron N. A. , McNutt Jr. R. L. , Wiedenbeck M. E. , Joyce C. , Cohen C. M. S. , Ebert R. W. , Dayeh M. A. , Allen R. C. , Davis A. J. , Krimigis S. M. , Leske R. A. , Matthaeus W. H. , Malandraki O. , Mewaldt R. A. , Labrador A. , Stone E. C. , Bale S. D. , Pulupa M. , MacDowall R. J. , Kasper J. C.
Published: February 2020

The Integrated Science Investigation of the Sun (IS⊙IS) suite on board NASA’s Parker Solar Probe (PSP) observed six distinct enhancements in the intensities of suprathermal-through-energetic (∼0.03–3 MeV nucleon−1) He ions associated with corotating or stream interaction regions (CIR or SIR) during its first two orbits. Our results from a survey of the time histories of the He intensities, spectral slopes, and anisotropies and the event-averaged energy spectra during these events show the following: (1) In the two strongest enhancements, seen at 0.35 and 0.85 au, the higher-energy ions arrive and maximize later than those at lower energies. In the event seen at 0.35 au, the He ions arrive when PSP was away from the SIR trailing edge and entered the rarefaction region in the high-speed stream. (2) The He intensities either are isotropic or show sunward anisotropies in the spacecraft frame. (3) In all events, the energy spectra between ∼0.2 and 1 MeV nucleon−1 are power laws of the form ∝E
−2. In the two strongest events, the energy spectra are well represented by flat power laws between ∼0.03 and 0.4 MeV nucleon−1 modulated by exponential rollovers between ∼0.4 and 3 MeV nucleon−1. We conclude that the SIR-associated He ions originate from sources or shocks beyond PSP’s location rather than from acceleration processes occurring at nearby portions of local compression regions. Our results also suggest that rarefaction regions that typically follow the SIRs facilitate easier particle transport throughout the inner heliosphere such that low-energy ions do not undergo significant energy loss due to adiabatic deceleration, contrary to predictions of existing models.
Parker Solar Probe Observations of a Dust Trail in the Orbit of (3200) Phaethon
Authors: Battams Karl , Knight Matthew M. , Kelley Michael S. P. , Gallagher Brendan M. , Howard Russell A. , Stenborg Guillermo
Published: February 2020

We present the identification and preliminary analysis of a dust trail following the orbit of (3200) Phaethon as seen in white-light images recorded by the Wide-field Imager for Parker Solar Probe (WISPR) instrument on the NASA Parker Solar Probe (PSP) mission. During PSP's first solar encounter in 2018 November, a dust trail following Phaethon’s orbit was visible for several days and crossing two fields of view. Preliminary analyses indicate this trail to have a visual magnitude of 15.8 ± 0.3 per pixel and a surface brightness of 25.0 mag arcsec−2 as seen by PSP/WISPR from a distance of ∼0.2 au from the trail. We estimate the total mass of the stream to be ∼(0.4–1.3) × 1012 kg, which is consistent with, though slightly underestimates, the assumed mass of the Geminid stream, but is far larger than the current dust production that Phaethon could support. Our results imply that we are observing a natural clustering of at least some portion of the Geminid meteor stream through its perihelion, as opposed to dust produced more recently from perihelion activity of Phaethon.
A first checklist of macrofungi for South Africa
Authors: Kinge Tonjock Rosemary , Goldman Gary , Jacobs Adriaana , Ndiritu George Gatere , Gryzenhout Marieka
Published: February 2020

Macrofungi are considered as organisms that form large fruiting bodies above or below the ground that are visible without the aid of a microscope. These fungi include most basidiomycetes and a small number of ascomycetes. Macrofungi have different ecological roles and uses, where some are edible, medicinal, poisonous, decomposers, saprotrophs, predators and pathogens, and they are often used for innovative biotechnological, medicinal and ecological applications. However, comprehensive checklists, and compilations on the diversity and distribution of mushrooms are lacking for South Africa, which makes regulation, conservation and inclusion in national biodiversity initiatives difficult. In this review, we compiled a checklist of macrofungi for the first time (excluding lichens). Data were compiled based on available literature in journals, books and fungorium records from the National Collection of Fungi. Even if the list is not complete due to numerous unreported species present in South Africa, it still represents an overview of the current knowledge of the macromycetes of South Africa. The list of names enables the assessment of gaps in collections and knowledge on the fungal biodiversity of South Africa, and downstream applications such as defining residency status of species. It provides a foundation for new names to be added in future towards developing a list that will be as complete as possible, and that can be used by a wide audience including scientists, authorities and the public.
Savage's P3 Is Redundant
Authors: Hartmann Lorenz
Published: February 2020

Savage (1954) provided the first axiomatic characterization of expected utility without relying on any given probabilities or utilities. It is the most famous preference axiomatization existing. This note shows that Savage's axiom P3 is implied by the other axioms, which reveals its redundancy. It is remarkable that this was not noticed before as Savage's axiomatization has been studied and taught by hundreds of researchers for more than six decades.
Information design and sequential screening with ex post participation constraint
Authors: Heumann Tibor
Published: February 2020

We study a principal–agent model. The parties are symmetrically informed at first; the principal then designs the process by which the agent learns his type and, concurrently, the screening mechanism. Because the agent can opt out of the mechanism ex post, it must leave him with nonnegative rents ex post. We characterize the profit‐maximizing mechanism. In that optimal mechanism, learning proceeds in continuous time and, at each moment, the agent learns a lower bound on his type. For each type, there is one of two possible outcomes: the type is allocated the efficient quantity or is left with zero rents ex post.
Coalition formation and history dependence
Authors: Dutta Bhaskar , Vartiainen Hannu
Published: February 2020

Farsighted formulations of coalitional formation, for instance, by Harsanyi and Ray and Vohra, have typically been based on the von Neumann–Morgenstern stable set. These farsighted stable sets use a notion of indirect dominance in which an outcome can be dominated by a chain of coalitional “moves” in which each coalition that is involved in the sequence
eventually stands to gain. Dutta and Vohra point out that these solution concepts do not require coalitions to make optimal moves. Hence, these solution concepts can yield unreasonable predictions. Dutta and Vohra restricted coalitions to hold common, history‐independent expectations that incorporate optimality regarding the continuation path. This paper extends the Dutta–Vohra analysis by allowing for history‐dependent expectations. The paper provides characterization results for two solution concepts that correspond to two versions of optimality. It demonstrates the power of history dependence by establishing nonemptyness results for all finite games as well as transferable utility partition function games. The paper also provides partial comparisons of the solution concepts to other solutions.
First‐price auctions with budget constraints
Authors: Kotowski Maciej H.
Published: February 2020

Consider a first‐price sealed‐bid auction with interdependent valuations and private budget constraints. Focusing on the two‐bidder case, we identify new sufficient conditions for the existence of a symmetric equilibrium in pure strategies. In equilibrium, agents may adopt discontinuous bidding strategies that result in a stratification of competition along the budget dimension. Private budgets can simultaneously lead to more aggressive bidding (a high‐budget agent leverages his wealth to outbid rivals) and more subdued bidding (competition becomes less intense among bidders at distinct budget levels). The presence of budget constraints may lead to multiple symmetric equilibria in the first‐price auction.
Agency business cycles
Authors: Golosov Mikhail , Menzio Guido
Published: February 2020

We develop a theory of endogenous and stochastic fluctuations in economic activity. Individual firms choose to randomize over firing or keeping workers who performed poorly in the past to give them an ex ante incentive to exert effort. Different firms choose to correlate the outcome of their randomization to reduce the probability with which they fire nonperforming workers. Correlated randomization leads to aggregate fluctuations. Aggregate fluctuations are endogenous—they emerge because firms choose to randomize and they choose to randomize in a correlated fashion—and they are stochastic—they are the manifestation of a randomization process. The hallmark of a theory of endogenous and stochastic fluctuations is that the stochastic process for aggregate “shocks” is an equilibrium object.
Collecting evidence on the use of parliamentary oversight tools: A South African case study
Authors: Janse van Rensburg Wilhelm , Vreÿ Francois , Neethling Theo
Published: February 2020

Background: Parliament, through its oversight function, plays a central role in holding the executive to account. In South Africa’s 2014 Defence Review policy document, it was stated that the ‘Defence Force is in a critical state of decline’. This brings about the question whether the South African Parliament effectively held the executive to account regarding developments around defence.Objectives: The article aims to gather evidence on the use of oversight tools by the South African Parliament over a 20-year period, within the post-1994 democratic dispensation, in order to determine the broader trajectory of parliamentary defence oversight.Method: To determine the trajectory of oversight, this article gathered evidence on the use of internationally recognised parliamentary oversight tools by South Africa’s two parliamentary defence committees from 1994 to 2014. The period allows for a 20-year review of oversight of defence, inclusive of four full parliamentary terms. Evidence was collected on parliamentary debates, questions, special inquiries, oversight visits and the use of external audits as oversight tools.Results: The article found that tools were used with varying degrees of success. Results for research on each oversight tool is discussed.Conclusion: Based on evidence on the use of oversight tools, this article concludes that over a 20-year period there was a declining trajectory in parliamentary oversight of the defence portfolio. The proven applicability of the criteria utilised in this article can serve to inform evaluations of the effectiveness of parliamentary oversight, specifically at committee level.
Usage of smart devices amongst medical practitioners in Universitas Academic Hospital
Authors: Xu Yeyang , Francis Zoë , Saleem Khayam , Sambujana Siphamandla , Molise Keitumetse , Molise Boitumelo , Pearce Nicholas , Joubert Gina
Published: February 2020

Background: There has been a rapid rise in the use of smart devices amongst medical practitioners throughout the world. This study aimed to identify how smart devices were being used by medical practitioners at the Universitas Academic Hospital (UAH), Bloemfontein, and the associated factors thereof. We also identified the views of medical practitioners regarding the usage of smart devices at their workplace.Methods: A prospective cross-sectional study was conducted. Anonymous questionnaires were distributed to medical practitioners working at UAH during weekly departmental meetings or monthly morbidity and mortality meetings. The following largest departments were included: Surgery, Anaesthetics, Paediatrics, Internal Medicine, Family Medicine, and Obstetrics and Gynaecology.Results: The response rate was 82.7% of those attending the meetings. All the respondents owned a smart device and brought it to their workplace. The most common applications used on these smart devices were that for drug references (65.9%), medical textbooks (63.6%) and medical calculators (58.1%). Significantly larger percentages of doctors aged 21–39 years compared with those aged 40–65 years used drug reference applications and medical calculators. A quarter (24.8%) of respondents communicated with patients through a smart device, 21.7% used an online storage platform to backup patient data, whilst 56.6% used their devices to store and view patient information. More than one-third (36.7%) agreed that smart devices threatened patient confidentiality, but the majority (58.8%) did not agree that these devices hinder patient communication. The majority felt that these devices improved both personal performance (69.2%) and patient care (79.0%).Conclusion: Smart devices usage is common in this setting. Hence, integration of such usage in medical curricula, discussion on professionalism, ethics and confidentiality in this context, and guidance from institutions and professional bodies become necessary.
Performance management, vigour, and training and development as predictors of job satisfaction in low-income workers
Authors: Maleka Molefe J. , Paul-Dachapalli Leigh-Anne , Ragadu Suzette C. , Schultz Cecilia M. , Van Hoek Lize
Published: February 2020

Orientation: New insights into how managers can develop strategies to enhance job satisfaction, how researchers can use a different approach when collecting data by conducting a survey at a mall instead of an organisation, and an understanding of the relationship between performance management, vigour, and training and development of low-income workers form part of the orientation of this article.Research purpose: The authors endeavoured to determine whether performance management, vigour, and training and development positively predicted the job satisfaction of low-income workers in the South African context.Motivation for the study: Little, if any, research exists about the relationships between performance management, vigour, and training and development as well as the job satisfaction of low-income workers in the South African context.Research approach/design and method: The research approach was quantitative, descriptive and causal in nature. This study mostly comprised the units of analysis, namely low-income workers who were under-researched in the South African context. Hence, 877 respondents were purposefully selected for this study.Main findings: The results showed that performance management was the highest predictor of job satisfaction. The second highest predictor of job satisfaction was vigour, and the third highest predictor of job satisfaction was training and development.Practical/managerial implications: This research will empower managers to develop strategies to enhance employees’ job satisfaction by paying attention to performance management, vigour, and training and development.Contribution/value-add: This study was conducted on an under-researched sample, at a mall and suggested vigour as an intrinsic variable to be included in the Herzberg job satisfaction model.
Robust Coordinated Design of Power System Stabilizer
and Excitation System Using Genetic Algorithm to
Enhance the Dynamic Stability of Al-Zara Thermal Power
Station Generation in Syria
Authors: Riad Al-Mustfa Riad Al-Mustfa
Published: February 2020

In this paper, a new formula of Power System Stabilizer
(PSS) was adopted. The design of PSS and Excitation system (an
Exciter) parameters is formulated as an optimization problem. A
continuous genetic algorithm (GA) is employed for searching
optimized parameters. A multi-objective function includes the
deviation in the oscillatory rotor speed of the generator is minimized
in time-domain to improve the stability performance of the system.
The design is performed using linearized models of a real thermal
power system, Al-Zara Thermal Power Station in Syria, at four
operating conditions and large perturbation. A cubic Hermite
interpolation technique is employed to determine the smoothest
possible curve that passes through its data set obtained by the GA. The
effectiveness and robustness of the designed stabilizer is investigated
and compared with conventional PSS. The simulation results show
that the GA stabilizer (GAPSS + GAExciter) are able to provide better
damping over a wide operating range with large perturbation and
improve the overall systems’ performance.
Geo/Geo/1/N Queue with In-Immune and Immune Service
Killing Discipline
Authors: Madhu Jain Madhu Jain
Published: February 2020

The present investigation studies a discrete time single
server queue with both positive and negative arrival streams in
accordance with removal of the customer from the end (RCE)-in
immune and immune service killing policy. This study is a
generalization of the queue with negative customers, wherein only
positive customers need a service and negative customers arriving to
the system can kill the already present positive customers from any
where in the queue, otherwise get lost. The concept of both in-immune
and immune service killing are taken into consideration. According to
the in-immune killing policy, the negative customer is allowed to kill
the most recent positive customer inspite of whether it is in service or
not, while the immune service killing discipline suggests that the
customer currently being served is immune from killing by the
negative arrival. We analyze a queue with geometric arrivals of both
positive and negative customers for a finite capacity system. The
stationary probability distribution and other performance measures are
derived in terms of the generating functions. The results so obtained
are validated by the numerical method based on successive over
relaxation method (SOR). We have also employed the neurro fuzzy
approach for exhibiting the approximate results for various
performance measures.
In-flight calibration results of the TROPOMI payload on-board theSentinel-5 Precursor satellite
Authors: Ludewig Antje , Kleipool Quintus , Bartstra Rolf , Landzaat Robin , Leloux Jonatan , Loots Erwin , Meijering Peter , van der Plas Emiel , Rozemeijer Nico , Vonk Frank , Veefkind Pepijn
Published: February 2020

Abstract. After the launch of the Sentinel-5 Precursor satellite on 13 October 2017 its single payload, the Tropospheric Monitoring Instrument (TROPOMI), was commissioned during 6 months. In this time the instrument was tested and calibrated extensively. During this phase the geolocation calibration was validated using a dedicated measurement zoom mode. With the help of spacecraft manoeuvres the solar angle dependence of the irradiance radiometry was calibrated for both internal diffusers. This improved the results that were obtained on-ground significantly. Furthermore the orbital and long term stability was tested for electronic gains, offsets, non-linearity, the dark current and the output of the internal light sources. The CCD output gain of the UV, UVIS and NIR detectors shows drifts over time which can be corrected for in the L1b processor. In-flight measurements also revealed inconsistencies of the radiometric calibration and degradation of the UV spectrometer. Degradation is also detected for the internal solar diffusers. Since the start of the nominal operations (E2) phase in orbit 2818 on 30 April 2018, regularly scheduled calibration measurements on the eclipse side of the orbit are used for monitoring and updates to calibration key data. This article reports on the main results of the commissioning phase, the in-flight calibration and on the instrument's stability since launch. Insights from commissioning and in-flight monitoring led to updates to the Level 1b processor and its calibration key data. The updated processor is planned to be used for nominal processing from 2020 on.