Sazuna/UAT_keywords huggingface dataset:
Parker Solar Probe Observations of a Dust Trail in the Orbit of (3200) Phaethon. 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.

Keywords: Near-Earth objects, Asteroids, Meteoroid dust clouds, Meteor streams, Meteor showers, Comets
Small, Low-energy, Dispersive Solar Energetic Particle Events Observed by Parker Solar Probe. The Energetic Particle Instrument-Low Energy (EPI-Lo) experiment has detected several weak, low-energy (∼30-300 keV nucleon-1) solar energetic particle (SEP) events during its first two closest approaches to the Sun, providing a unique opportunity to explore the sources of low-energy particle acceleration. As part of the Parker Solar Probe (PSP) Integrated Science Investigation of the Sun (IS⊙IS) suite, EPI-Lo was designed to investigate the physics of energetic particles; however, in the special lowest-energy "time-of-flight only" product used in this study, it also responds to solar photons in a subset of approximately sunward-looking apertures lacking special light-attenuating foils. During the first three perihelia, in a frame rotating with the Sun, PSP undergoes retrograde motion, covering a 17° heliographic longitudinal range three times during the course of the ∼11-day perihelion passes, permitting a unique spatial and temporal study into the location, correlation, and persistence of previously unmeasurable SEPs. We examine the signatures of these SEPs (during the first PSP perihelion pass only) and the connection to possible solar sources using remote observations from the Solar Dynamics Observatory (SDO), the Solar TErrestrial RElations Observatory (STEREO), and the ground-based Global Oscillation Network Group (GONG). The orientation of the Sun relative to STEREO, SDO, and GONG makes such identifications challenging, but we do have several candidates, including an equatorial coronal hole at a Carrington longitude of ∼335°. To analyze observations from EPI-Lo, which is a new type of particle instrument, we examine instrumental effects and provide a preliminary separation of the ion signal from the photon background.

Keywords: Michelson interferometers, Space vehicle instruments, Space probes, Solar flares, Solar extreme ultraviolet emission, Solar energetic particles, The Sun, Quiet sun, Interplanetary particle acceleration, Solar filament eruptions, Solar coronal mass ejections, Solar telescopes
Ion-scale Electromagnetic Waves in the Inner Heliosphere. Understanding the physical processes in the solar wind and corona that actively contribute to heating, acceleration, and dissipation is a primary objective of NASA's Parker Solar Probe (PSP) mission. Observations of circularly polarized electromagnetic waves at ion scales suggest that cyclotron resonance and wave-particle interactions are dynamically relevant in the inner heliosphere. A wavelet-based statistical study of circularly polarized events in the first perihelion encounter of PSP demonstrates that transverse electromagnetic waves at ion resonant scales are observed in 30-50% of radial field intervals. Average wave amplitudes of approximately 4 nT are measured, while the mean duration of wave events is on the order of 20 s; however, long-duration wave events can exist without interruption on hour-long timescales. Determination of wave vectors suggests propagation parallel/antiparallel to the mean magnetic field. Though ion-scale waves are preferentially observed during intervals with a radial mean magnetic field, we show that measurement constraints, associated with single spacecraft sampling of quasi-parallel waves superposed with anisotropic turbulence, render the measured coherent ion-wave spectrum unobservable when the mean magnetic field is oblique to the solar wind flow; these results imply that the occurrence of coherent ion-scale waves is not limited to a radial field configuration. The lack of radial scaling of characteristic wave amplitudes and duration suggests that the waves are generated in situ through plasma instabilities. Additionally, observations of proton distribution functions indicate that temperature anisotropy may drive the observed ion-scale waves.

Keywords: Space plasmas, Interplanetary turbulence, Solar coronal heating, Solar wind, Plasma astrophysics
Cross Helicity Reversals in Magnetic Switchbacks. 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 encounter is a new observation, and their precise origin is still unknown. By analyzing these MHD invariants as a function of the wavelet scale, we show that magnetohydrodynamic (MHD) waves do indeed follow the local mean magnetic field through switchbacks, with a net Elsässer flux propagating inward during the field reversal and that they, therefore, must be local kinks in the magnetic field and not due to small regions of opposite polarity on the surface of the Sun. Such observations are important to keep in mind as computing cross helicity without taking into account the effect of switchbacks may result in spurious underestimation of σc as PSP gets closer to the Sun in later orbits.

Keywords: Interplanetary turbulence, Space plasmas, Alfven waves, Heliosphere
Switchbacks in the Solar Magnetic Field: Their Evolution, Their Content, and Their Effects on the Plasma. 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 divergence of the Poynting flux from outside to inside the switchback, which produces a loss of electromagnetic energy on switchback entry and recovery of that energy on exit, with the lost energy appearing in the plasma flow. Switchbacks contain 0.3-10 Hz waves that may result from currents and the Kelvin-Helmholtz instability that occurs at the switchback boundaries. These waves may combine with lower frequency magnetohydrodynamic waves to heat the plasma.

Keywords: Solar physics, Solar wind, Solar magnetic fields
Source and Propagation of a Streamer Blowout Coronal Mass Ejection Observed by the Parker Solar Probe. In the first orbit of the Parker Solar Probe (PSP), in situ thermal plasma and magnetic field measurements were collected as close as 35 RSun from the Sun, an environment that had not been previously explored. During the first orbit of PSP, the spacecraft flew through a streamer blowout coronal mass ejection (SBO-CME) on 2018 November 11 at 23:50 UT as it exited the science encounter. The SBO-CME on November 11 was directed away from the Earth and was not visible by L1 or Earth-based telescopes due to this geometric configuration. However, PSP and the STEREO-A spacecraft were able to make observations of this slow (V ≈ 380 km s-1) SBO-CME. Using the PSP data, STEREO-A images, and Wang-Sheeley-Arge model, the source region of the CME is found to be a helmet streamer formed between the northern polar coronal hole and a mid-latitude coronal hole. Using the YGUAZU-A model, the propagation of the CME is traced from the source at the Sun to PSP. This model predicts the travel time of the flux rope to the PSP spacecraft as 30 hr, which is within 0.33 hr of the actual measured arrival time. The in situ Solar Wind Electrons Alphas and Protons data were examined to determine that no shock was associated with this SBO-CME. Modeling of the SBO-CME shows that no shock was present at PSP; however, at other positions along the SBO-CME front, a shock could have formed. The geometry of the event requires in situ and remote sensing observations to characterize the SBO-CME and further understand its role in space weather.

Keywords: Space weather, Solar coronal mass ejections
Proton Temperature Anisotropy Variations in Inner Heliosphere Estimated with the First Parker Solar Probe Observations. We present a technique for deriving the temperature anisotropy of solar wind protons observed by the Parker Solar Probe (PSP) mission in the near-Sun solar wind. The radial proton temperature measured by the Solar Wind Electrons, Alphas, and Protons (SWEAP) Solar Probe Cup is compared with the orientation of local magnetic field measured by the FIELDS fluxgate magnetometer, and the proton temperatures parallel and perpendicular to the magnetic field are extracted. This procedure is applied to different data products, and the results are compared and optimum timescales for data selection and trends in the uncertainty in the method are identified. We find that the moment-based proton temperature anisotropy is more physically consistent with the expected limits of the mirror and firehose instabilities, possibly because the nonlinear fits do not capture a significant non-Maxwellian shape to the proton velocity distribution function near the Sun. The proton beam has a small effect on total proton temperature anisotropy owing to its much smaller density relative to the core compared to what was seen by previous spacecraft farther from the Sun. Several radial trends in the temperature components and the variation of the anisotropy with parallel plasma beta are presented. Our results suggest that we may see stronger anisotropic heating as PSP moves closer to the Sun, and that a careful treatment of the shape of the proton distribution may be needed to correctly describe the temperature.

Keywords: Space plasmas, Solar coronal heating, Solar wind
MHD Mode Composition in the Inner Heliosphere from the Parker Solar Probe’s First Perihelion. Field and plasma variations during the first perihelion pass of the Parker Solar Probe (PSP) from 53 into 35 solar radii (R  S ) from the Sun and over a frequency range in the spacecraft frame (f SC) from 0.0002 to 0.2 Hz are decomposed into constituent magnetohydrodynamic (MHD) modes. The analysis operates on measurements of the MHD variables recorded between impulsive, large amplitude rotations of the magnetic field to reveal the dominance of a broad spectrum of shear Alfvén waves propagating antiparallel (backward) to the background magnetic field ( B 0) with a significant fraction of spectral energy density in the backward slow mode and, to a lesser extent, fast mode waves. While all three MHD modes provide Poynting flux directed outward from the Sun the impulsive rotations of B 0 from inward to outward radial orientations provide intervals of outward and inward propagation in the plasma frame, respectively. This morphology is suggestive of outward wave propagation from a near Sun source along kinked field lines that provide alternating radial B 0 orientations as the magnetic field is advected with the flow over the spacecraft. Shear Alfvén and slow mode spectral energy density is generally largest within intervals of reversed radial B 0, while the fast mode tends to occur outside these regions, albeit with lower intensity. The spectral energy density in the forward propagating modes increases with f SC above 0.01 Hz, which is suggestive of back scatter in the plasma frame of the dominant backward modes from the radial field reversals and associated inhomogeneities of the embedded plasmas.

Keywords: Slow solar wind, Solar coronal holes, Magnetohydrodynamics
Modeling the Early Evolution of a Slow Coronal Mass Ejection Imaged by the Parker Solar Probe. During its first solar encounter, the Parker Solar Probe (PSP) acquired unprecedented up-close imaging of a small coronal mass ejection (CME) propagating in the forming slow solar wind. The CME originated as a cavity imaged in extreme ultraviolet that moved very slowly (&lt;50 km s-1) to 3-5 solar radii (R ⊙), where it then accelerated to supersonic speeds. We present a new model of an erupting flux rope (FR) that computes the forces acting on its expansion with a computation of its internal magnetic field in three dimensions. The latter is accomplished by solving the Grad-Shafranov equation inside two-dimensional cross sections of the FR. We use this model to interpret the kinematic evolution and morphology of the CME imaged by PSP. We investigate the relative role of toroidal forces, momentum coupling, and buoyancy for different assumptions on the initial properties of the CME. The best agreement between the dynamic evolution of the observed and simulated FR is obtained by modeling the two-phase eruption process as the result of two episodes of poloidal flux injection. Each episode, possibly induced by magnetic reconnection, boosted the toroidal forces accelerating the FR out of the corona. We also find that the drag induced by the accelerating solar wind could account for about half of the acceleration experienced by the FR. We use the model to interpret the presence of a small dark cavity, clearly imaged by PSP deep inside the CME, as a low-density region dominated by its strong axial magnetic fields.

Keywords: Slow solar wind, Solar coronal transients, Solar coronal streamers
Operational Modeling of Heliospheric Space Weather for the Parker Solar Probe. The interpretation of multi-spacecraft heliospheric observations and three-dimensional reconstruction of the structured and evolving solar wind with propagating and interacting coronal mass ejections (CMEs) is a challenging task. Numerical simulations can provide global context and suggest what may and may not be observed. The Community Coordinated Modeling Center (CCMC) provides both mission science and space weather support to all heliospheric missions. Currently, this is realized by real-time simulations of the corotating and transient disturbances by the WSA-ENLIL-Cone model. We have simulated the heliospheric space weather relevant to the Parker Solar Probe (PSP) mission since 2018 September and provided numerical results to our colleagues analyzing in situ measurements published in the ApJS Special Issue. In this paper, we do not analyze PSP data, but we present recent updates in simulating the background solar wind and compare them with an existing operational model around the first PSP Perihelion, from 2018 October to 2018 December. We introduce new tools that assist in the interpretation of remote observations and in situ measurements useful for PSP and other missions, and for predicting heliospheric space weather. We also use this opportunity to evaluate recent improvements in the WSA and ADAPT-WSA coronal models that are being transitioned and considered to be transitioned, respectively, to operations. Finally, we simulate CME-like hydrodynamic ejecta with various parameters and calculated synthetic white-light images that can be used for “mid-course” correction of operational predictions.

Keywords: Space weather, Solar wind, Solar coronal mass ejections, Magnetohydrodynamical simulations
The Solar Probe ANalyzers—Electrons on the Parker Solar Probe. Electrostatic analyzers of different designs have been used since the earliest days of the space age, beginning with the very earliest solar-wind measurements made by Mariner 2 en route to Venus in 1962. The Parker Solar Probe (PSP) mission, NASA’s first dedicated mission to study the innermost reaches of the heliosphere, makes its thermal plasma measurements using a suite of instruments called the Solar Wind Electrons, Alphas, and Protons (SWEAP) investigation. SWEAP’s electron PSP Analyzer (Solar Probe ANalyzer-Electron (SPAN-E)) instruments are a pair of top-hat electrostatic analyzers on PSP that are capable of measuring the electron distribution function in the solar wind from 2 eV to 30 keV. For the first time, in situ measurements of thermal electrons provided by SPAN-E will help reveal the heating and acceleration mechanisms driving the evolution of the solar wind at the points of acceleration and heating, closer than ever before to the Sun. This paper details the design of the SPAN-E sensors and their operation, data formats, and measurement caveats from PSP’s first two close encounters with the Sun.

Keywords: Space plasmas, Solar coronal heating, Solar wind, Solar instruments
Superhydrogenated Polycyclic Aromatic Hydrocarbon Molecules: Vibrational Spectra in the Infrared. Superhydrogenated polycyclic aromatic hydrocarbons (PAHs) may be present in H-rich and ultraviolet-poor benign regions. The addition of excess H atoms to PAHs converts the aromatic bonds into aliphatic bonds, the strongest of which falls near 3.4 μm. Therefore, superhydrogenated PAHs are often hypothesized to be a carrier of the 3.4 μm emission feature that typically accompanies the stronger 3.3 μm aromatic C-H stretching feature. To assess this hypothesis, we use density function theory to compute the infrared (IR) vibrational spectra of superhydrogenated PAHs and their ions of various sizes (ranging from benzene and naphthalene to perylene and coronene) and of various degrees of hydrogenation. For each molecule, we derive the intrinsic oscillator strengths of the 3.3 μm aromatic C-H stretch (A_{3.3}) and the 3.4 μm aliphatic C-H stretch (A_{3.4}). By comparing the computationally derived mean ratio of &lt; {A}_{3.4}/{A}_{3.3} &gt; ≈ 1.98 with the mean ratio of the observed intensities &lt; I_{3.4}/I_{3.3} &gt; ≈0.12, we find that the degree of superhydrogenation - the fraction of carbon atoms attached with extra hydrogen atoms - is only ∼2.2% for neutral PAHs, which predominantly emit the 3.3 and 3.4 μm features. We also determine for each molecule the intrinsic band strengths of the 6.2 μm aromatic C-C stretch (A_{6.2}) and the 6.85 μm aliphatic C-H deformation (A_{6.85}). We derive the degree of superhydrogenation from the mean ratio of the observed intensities &lt; {I}_{6.85}/{I}_{6.2} &gt; ≲ 0.10 and &lt; {A}_{6.85}/{A}_{6.2} &gt; ≈ 1.53 for neutrals and &lt; {A}_{6.85}/{A}_{6.2}&gt; ≈ 0.56 for cations to be ≲3.1% for neutrals and ≲8.6% for cations. We conclude that astrophysical PAHs are primarily aromatic and are only marginally superhydrogenated.

Keywords: Interstellar line emission, Polycyclic aromatic hydrocarbons, Line intensities
Self-gravitational Force Calculation of Second-order Accuracy Using the Multigrid Method on Nested Grids. We present a simple and effective multigrid-based Poisson solver of second-order accuracy in both gravitational potential and forces in terms of the one, two, and infinity norms. The method is especially suitable for numerical simulations using nested mesh refinement. The Poisson equation is solved from coarse to fine levels using a one-way interface scheme. We introduce antisymmetrically linear interpolation for evaluating the boundary conditions across the multigrid hierarchy. The spurious forces commonly observed at the interfaces between refinement levels are effectively suppressed. We validate the method using two- and three-dimensional density-force pairs that are sufficiently smooth for probing the order of accuracy.

Keywords: Gravitation, Computational methods
Kinematic Signatures of Reverberation Mapping of Close Binaries of Supermassive Black Holes in Active Galactic Nuclei. II. Atlas of Two-dimensional Transfer Functions. Most large galaxies harbor supermassive black holes (SMBHs) in their centers, and galaxies merge. Consequently, binary SMBHs should be common in galactic nuclei. However, close binaries of SMBH (CB-SMBHs) with subparsec separation cannot be imaged directly using current facilities. Some indirect signatures, such as periodic signals in light curves and double peaks in the emission-line profile, have been used to find CB-SMBH candidates, but ambiguities still exist and no definitive conclusions can be made. We have recently proposed a new method focusing on kinematic signatures that can be derived from reverberation mapping of CB-SMBHs, one that offers a promising avenue to address this important problem. In this paper, we calculated models for a wide range of parameters, but broad-line regions of two BHs are close but still not merged. The purpose of this supplementary paper is to provide an atlas of two-dimensional transfer functions of CB-SMBHs with a wide range of orbital and geometrical parameters to aid more efficient identification of CB-SMBH candidates in reverberation mapping data.

Keywords: Supermassive black holes, Reverberation mapping, Active galactic nuclei
The Effect of Chemisorption on the Chemical Evolution of Star-forming Regions. We have studied the production of simple molecules on interstellar dust grains involving strong bonding via chemisorption on a graphite surface. Two classes of chemical simulations were run: models under isothermal conditions at temperatures from 150 to 400 K at 25 K intervals, and warm-up models starting at 10 K. For the isothermal models, physisorption does not occur appreciably, whereas for the warm-up models, it dominates at the lower temperatures before thermal desorption becomes rapid. We have made several simple approximations to determine what role, if any, chemisorption can play in the surface chemistry that occurs at temperatures above which icy mantles no longer cover the surface of dust grains. Our major finding is that the importance of chemisorption is greatly dependent on the efficiency of adsorption. Models having the lowest adsorption barrier show maximum abundances of chemisorbed species. Species such as CO, which are very efficiently formed in the gas phase at almost all temperatures (10-400 K), will not be strongly impacted by the existence of chemisorbed species. However, chemisorbed CO can achieve a reasonably high abundance (∼10-6). Species such as C2H2 and NH3, which are less efficiently formed compared with CO in the gas phase, may show a change in their gas-phase abundance due to chemisorption. Several examples of this class of species can also show reasonably high abundances on grain surfaces due to chemisorption when the adsorption barrier is low.

Keywords: Interstellar molecules, Interstellar dust, Astrochemistry, Interstellar medium