Sazuna/UAT_keywords huggingface dataset:
On the Relation between Flare and CME during GLE-SEP and Non-GLE-SEP Events. Association of solar flares and coronal mass ejections (CMEs) with ground-level enhancement (GLE) is a recognized fact, but questions arise when a similar association is observed for non-GLEs. In this respect, we carry out a detailed study of the relation between flare fluences (ϕ J m-2) and CME speeds (V cme km s-1) during some selected GLEs and non-GLEs. As we found, most of the data points of ϕ (J m-2) and V cme (km s-1) of GLEs follow a near-linear trend, with the ϕ (J m-2) increasing as the V cme (km s-1) increases, resulting in a strong positive correlation (r ≥ 0.82), while the correlation (r ≤ 0.47) remains weak for non-GLEs. For any exceptional GLE, the ϕ (J m-2) and V cme (km s-1) that do not maintain a near-linear trend over the whole flare phase do maintain at least a minimum rational proportionality over the flare rise phase, whereas this characteristic was not generally observed for non-GLEs. Although the ϕ (J m-2) and V cme (km s-1) of some non-GLEs show a trend similar to those of GLEs, they indeed originated over the flare impulsive phases concomitant with coronal shock manifested in m type II bursts, while GLEs originated over the flare initial phase before the m type II. Flare peak fluences (ϕ pk J m-2) and V cme (km s-1) maintain weak correlation for both GLEs and non-GLEs, likely because the CME main acceleration ceases around the flare peak. However, though the ϕ pk (J m-2) governs the flare total fluence, it does not blur the correlation between the fluence over the flare rise phase (ϕ  r  J m-2) and V cme (km s-1), indicating that the flare peak/strength does not control the GLE occurrence.

Keywords: The Sun
Changes in Solar Rotation over Two Solar Cycles. We use helioseismic data from ground- and space-based instruments to analyze how solar rotation has changed since the beginning of solar Cycle 23 with emphasis on studying the differences between Cycles 23 and 24. We find that the nature of solar rotation is indeed different for the two cycles. While the changes in the latitudinally independent component follows solar-cycle indices, some of the other components have a more complicated behavior. There is a substantial change in the behavior of the solar zonal flows and their spatial gradients too. While the zonal flows in Cycle 24 are weaker in general than those in Cycle 23, there are clear signs of the emergence of Cycle 25. We have also investigated the properties of the solar tachocline, in particular, its position, width, and the change (or jump) in the rotation rate across it. We find significant temporal variation in the change of the rotation rate across the tachocline. We also find that the changes in solar Cycle 24 were very different from those of Cycle 23. We do not find any statistically significant change in the position or the width of the tachocline.

Keywords: Solar cycle, Solar rotation, Solar interior, Helioseismology, The Sun, Stellar activity, Solar oscillations
New Spatially Resolved Imaging of the SR 21 Transition Disk and Constraints on the Small-grain Disk Geometry. We present new 0.6-4 μm imaging of the SR 21 transition disk from Keck/NIRC2 and Magellan/MagAO. The protoplanetary disk around SR 21 has a large (∼30-40 au) clearing first inferred from its spectral energy distribution and later detected in submillimeter imaging. Both the gas and small dust grains are known to have a different morphology, with an inner truncation in CO at ∼7 au, and micron-sized dust detected within the millimeter clearing. Previous near-infrared imaging could not distinguish between an inner dust disk with a truncation at ∼7 au or one that extended to the sublimation radius. The imaging data presented here require an inner dust disk radius of a few au, and complex structure such as a warp or spiral. We present a parametric warped disk model that can reproduce the observations. Reconciling the images with the spectral energy distribution gathered from the literature suggests grain growth to ≳2-5 μm within the submillimeter clearing. The complex disk structure and possible grain growth can be connected to dynamical shaping by a giant-planet-mass companion, a scenario supported by previous observational and theoretical studies.

Keywords: Optical interferometry, Direct imaging, Protoplanetary disks, Planet formation
Heliosheath Properties Measured from a Voyager 2 to Voyager 1 Transient. In mid-2012, a global merged interaction region (GMIR) observed by Voyager 2 crossed through the heliosheath and collided with the heliopause, generating a pressure pulse that propagated into the very local interstellar medium. The effects of the transmitted wave were seen by Voyager 1 just 93 days after its own heliopause crossing. The passage of the transient was accompanied by long-lasting decreases in Galactic cosmic ray intensities that occurred from ∼2012.55 to ∼2013.35 and ∼2012.91 to ∼2013.70 at Voyager 2 and Voyager 1, respectively. Omnidirectional (≳20 MeV) proton-dominated measurements from each spacecraft’s Cosmic Ray Subsystem reveal a remarkable similarity between these causally related events, with a correlation coefficient of 91.2% and a time lag of 130 days. Knowing the locations of the two spacecraft, we use the observed time delay to calculate the GMIR’s average speed through the heliosheath (inside the heliopause) as a function of temperature in the very local interstellar medium. This, combined with particle, field, and plasma observations, enables us to infer previously unmeasured properties of the heliosheath, including a range of sound speeds and total effective pressures. For a nominal temperature of ∼20,000 K just outside the heliopause, we find a sound speed of 314 ± 32 km s-1 and total effective pressure of 267 ± 55 fPa inside the heliopause. We compare these results with the Interstellar Boundary Explorer’s data-driven models of heliosheath pressures derived from energetic neutral atom fluxes (the globally distributed flux) and present them as additional evidence that the heliosheath’s dynamics are driven by suprathermal energetic processes.

Keywords: Heliopause, Interstellar dynamics, Heliosphere, Shocks, Solar wind, Plasma astrophysics, Interstellar plasma, Galactic cosmic rays, Pickup ions, Interstellar medium, Solar activity, Heliosheath
Modeling UV Radiation Feedback from Massive Stars. III. Escape of Radiation from Star-forming Giant Molecular Clouds. Using a suite of radiation hydrodynamic simulations of star cluster formation in turbulent clouds, we study the escape fraction of ionizing (Lyman continuum) and non-ionizing (FUV) radiation for a wide range of cloud masses and sizes. The escape fraction increases as H II regions evolve and reaches unity within a few dynamical times. The cumulative escape fraction before the onset of the first supernova explosion is in the range 0.05-0.58 this is lower for higher initial cloud surface density, and higher for less massive and more compact clouds due to rapid destruction. Once H II regions break out of their local environment, both ionizing and non-ionizing photons escape from clouds through fully ionized, low-density sight lines. Consequently, dust becomes the dominant absorber of ionizing radiation at late times, and the escape fraction of non-ionizing radiation is only slightly larger than that of ionizing radiation. The escape fraction is determined primarily by the mean &lt; τ &gt; and width σ of the optical-depth distribution in the large-scale cloud, increasing for smaller &lt; τ &gt; and/or larger σ. The escape fraction exceeds (sometimes by three orders of magnitude) the naive estimate {e}-&lt; τ &gt;  due to the nonzero σ induced by turbulence. We present two simple methods to estimate, within ∼20%, the escape fraction of non-ionizing radiation using the observed dust optical depth in clouds projected on the plane of sky. We discuss implications of our results for observations, including inference of star formation rates in individual molecular clouds and accounting for diffuse ionized gas on galactic scales.

Keywords: Interstellar radiation field, Giant molecular clouds, H II regions, Interstellar medium, Astrophysical fluid dynamics, Star clusters
The Implications of Local Fluctuations in the Galactic Midplane for Dynamical Analysis in the Gaia Era. Orbital properties of stars, computed from their six-dimensional phase-space measurements and an assumed Galactic potential, are used to understand the structure and evolution of the Galaxy. Stellar actions, computed from orbits, have the attractive quality of being invariant under certain assumptions and are therefore used as quantitative labels of a star’s orbit. We report a subtle but important systematic error that is induced in the actions as a consequence of local midplane variations expected for the Milky Way. This error is difficult to model because it is non-Gaussian and bimodal, with neither mode peaking on the null value. An offset in the vertical position of the Galactic midplane of ∼15 pc for a thin disk-like orbit or ∼120 pc for a thick disk-like orbit induces a 25% systematic error in the vertical action J  z . In Feedback in Realistic Environments simulations of Milky Way-mass galaxies, these variations are on the order of ∼100 pc at the solar circle. From observations of the mean vertical velocity variation of ∼5-10 km s-1 with radius, we estimate that the Milky Way midplane variations are ∼60-170 pc, consistent with three-dimensional dust maps. Action calculations and orbit integrations, which assume the global and local midplanes are identical, are likely to include this induced error, depending on the volume considered. Variation in the local standard of rest or distance to the Galactic center causes similar issues. The variation of the midplane must be taken into account when performing dynamical analysis across the large regions of the disk accessible to Gaia and future missions.

Keywords: Orbits, Galaxy structure, Milky Way dynamics, Stellar dynamics, Milky Way disk, Milky Way evolution
Stereoscopic Observations of an Erupting Mini-filament-driven Two-sided-loop Jet and the Applications for Diagnosing a Filament Magnetic Field. Ubiquitous solar jets or jet-like activities are generally regarded as an important source of energy and mass input to the upper solar atmosphere and the solar wind. However, their triggering and driving mechanisms are not completely understood. By taking advantage of stereoscopic observations with high temporal and spatial resolutions taken by the Solar Dynamic Observatory (SDO) and the Solar Terrestrial Relations Observatory (STEREO), we report an intriguing two-sided-loop jet that occurred on 2013 June 02, and was dynamically associated with the eruption of a mini-filament below an overlying large filament. Additionally, two distinct reconnection processes are identified during the formation stage. The SDO observations reveal that the two-sided-loop jet showed a concave shape with a projection speed of about 80-136 km s-1. From the other view angle, the STEREO observations clearly showed that the trajectories of the two arms of the two-sided-loop were along the cavity magnetic field lines hosting the large filament. Contrary to the well-accepted theoretical model, the present observation sheds new light on our understanding of the formation mechanism of two-sided-loop jets. Moreover, the eruption of the two-sided-loop jet not only supplied mass to the overlying large filament, but also provided a rare opportunity to diagnose the magnetic structure of the overlying large filament via the method of three-dimensional reconstruction.

Keywords: Solar flares, Solar filaments, Solar magnetic fields, Solar coronal mass ejections, Solar activity
Dynamical Masses for the Hyades Binary 80 Tauri. The empirical mass-luminosity relation in the Hyades cluster rests on dynamical mass determinations for five binary systems, of which one is eclipsing and the other four are visual or interferometric binaries. The last one was identified and first measured more than 20 yr ago. Here we present dynamical mass measurements for a new binary system in the cluster, 80 Tau, which is also a visual pair with a much longer orbital period of about 170 yr. Although we lack the radial-velocity information that has enabled the individual mass determinations in all of the previous binaries, we show that it is still possible to derive the component masses for 80 Tau using only astrometric observations. This is enabled by the accurate proper motion measurements from the Hipparcos and Gaia missions, which constrain the orbital acceleration in the plane of the sky. Separate proper motion values from Gaia for the primary and secondary provide a direct constraint on the mass ratio. Our mass measurements, {M}{{A}}={1.63}-0.13+0.30 {M}⊙  and {M}{{B}}={1.11}-0.14+0.21 {M}⊙ , are consistent with the mass-luminosity relation defined by the five previously known systems, which in turn is in good agreement with current models of stellar evolution.

Keywords: Visual binary stars
Multiband Optical Light Curves of Black-widow Pulsars. We collect new and archival optical observations of nine “black-widow” millisecond pulsar binaries. New measurements include direct imaging with the Keck, Gemini-S, MDM, and Las Cumbres Observatory 2 m telescopes. This is supplemented by synthesized colors from Keck long-slit spectra. Four black-widow optical companions are presented here for the first time. Together these data provide multicolor photometry covering a large fraction of the orbital phase. We fit these light curves with a direct (photon) heating model using a version of the ICARUS light-curve modeling code. The fits provide distance and fill-factor estimates, inclinations, and heating powers. We compare the heating powers with the observed GeV luminosities, noting that the ratio is sensitive to pulsar distance and to the gamma-ray beaming. We make a specific correction for “outer gap” model beams, but even then some sources are substantially discrepant, suggesting imperfect beaming corrections and/or errors in the fit distance. The fits prefer large metal abundance for half of the targets, a reasonable result for these wind-stripped secondaries. The companion radii indicate substantial Roche-lobe filling, f  c  ≈ 0.7-1 except for PSR J0952-0607, which with f  c  &lt; 0.5 has a companion density ρ ≈ 10 g cm-3, suggesting unusual evolution. We note that the direct-heating fits imply large heating powers and rather small inclinations, and we speculate that unmodeled effects can introduce such bias.

Keywords: Close binary stars, Millisecond pulsars, Pulsars
The Fundamental Vibrational Frequencies and Spectroscopic Constants of the Dicyanoamine Anion, NCNCN<SUP>-</SUP> (C<SUB>2</SUB>N<SUB>3</SUB> <SUP>-</SUP>): Quantum Chemical Analysis for Astrophysical and Planetary Environments. Detecting anions in space has relied on a strong collaboration between theoretical and laboratory analyses to measure rotational spectra and spectroscopic constants to high accuracy. The advent of improved quantum chemical tools operating at higher accuracy and reduced computational cost is a crucial solution for the fundamental characterization of astrophysically relevant anions and their detection in the interstellar medium (ISM) and planetary atmospheres. In this context, we have turned toward the quantum chemical analysis of the penta-atomic dicyanoamine anion NCNCN- ({{{C}}}2{{{{N}}}3}-), a structurally bent and polar compound. We have performed high-level coupled cluster theory quartic force field computations of {{{C}}}2{{{{N}}}3}- satisfying both computational cost and accuracy conditions. We provide for the first time accurate spectroscopic constants and vibrational frequencies for this ion. In addition to exhibiting various Fermi resonances, {{{C}}}2{{{{N}}}3}- displays a bright ν 2 (2130.9 cm-1) and a less intense ν 1 (2190.7 cm-1) fundamental vibrational frequency, making for strong markers for future infrared observations &lt;5 μm. We have also determined near-IR overtone and combination bands of the bright fundamentals for which the 2ν 2 at 4312.1 cm-1 (2.319 μm) is the best candidate. {{{C}}}2{{{{N}}}3}- could potentially exist and be detected in nitrogen-rich environments of the ISM such as IRC +10216 and other carbon-rich circumstellar envelopes, or in the atmosphere of Saturn’s moon Titan, where advanced N-based reactions may lead to its formation.

Keywords: Interstellar molecules, Molecular gas, Planetary atmospheres, Interstellar medium
A Prospective New Diagnostic Technique for Distinguishing Eruptive and Noneruptive Active Regions. Active regions are the source of the majority of magnetic flux rope ejections that become coronal mass ejections (CMEs). To identify in advance which active regions will produce an ejection is key for both space weather prediction tools and future science missions such as Solar Orbiter. The aim of this study is to develop a new technique to identify which active regions are more likely to generate magnetic flux rope ejections. The new technique will aim to (i) produce timely space weather warnings and (ii) open the way to a qualified selection of observational targets for space-borne instruments. We use a data-driven nonlinear force-free field (NLFFF) model to describe the 3D evolution of the magnetic field of a set of active regions. We determine a metric to distinguish eruptive from noneruptive active regions based on the Lorentz force. Furthermore, using a subset of the observed magnetograms, we run a series of simulations to test whether the time evolution of the metric can be predicted. The identified metric successfully differentiates active regions observed to produce eruptions from the noneruptive ones in our data sample. A meaningful prediction of the metric can be made between 6 and 16 hr in advance. This initial study presents an interesting first step in the prediction of CME onset using only line-of-sight magnetogram observations combined with NLFFF modeling. Future studies will address how to generalize the model such that it can be used in a more operational sense and for a variety of simulation approaches.

Keywords: Solar active region magnetic fields, Solar flares, Space weather, Solar active regions, Solar magnetic fields, Solar coronal mass ejections, Solar corona, Solar activity
Redshift Horizon for Detecting the First Galaxies in Far-infrared Surveys. We explore the possibility of detecting the first galaxies with the next generation of space-based far-infrared (FIR) telescopes by applying an analytical model of primordial dust emission. Our results indicate that FIR/submillimeter sources at z ≳ 7 will experience a strong negative K-correction. Systems of a given virial mass would exhibit larger dust luminosities at higher z, as a consequence of the increase in dust temperature driven by the higher temperature floor set by the cosmic microwave background. In addition, high-z systems are more concentrated, which enhances the heating efficiency associated with stellar radiation. By analyzing source densities as a function of z, and considering survey areas of 0.1 and 10 deg2, we find that the redshift horizon for detecting at least one source would be above z ∼ 7 for instrument sensitivities ≲0.1-0.5 and ≲0.5-3.0 μJy, respectively, with the exact values depending on the nature of primordial dust. However, galaxy populations with higher than typical metallicities, star formation efficiencies, and/or dust-to-metal ratios could relax such sensitivity requirements. In addition, the redshift horizon shows a significant dependence on the nature of primordial dust. We conclude that future FIR campaigns could play a crucial role in exploring the nature of dust and star formation in the early universe.

Keywords: Cosmology, Dust continuum emission, High-redshift galaxies, Galaxy evolution
A Parameter Space Exploration of Galaxy Cluster Mergers. II. Effects of Magnetic Fields. The hot intracluster plasma in clusters of galaxies is weakly magnetized. Mergers between clusters produce gas compression and motions that can increase the magnetic field strength. In this work, we perform high-resolution nonradiative magnetohydrodynamics simulations of binary galaxy cluster mergers with magnetic fields, to examine the effects of these motions on the magnetic field configuration and strength, as well as the effect of the field on the gas itself. Our simulations sample a parameter space of initial mass ratios and impact parameters. During the first core passage of mergers, the magnetic energy increases via gas compression. After this, shear flows produce temporary, megaparsec-scale, strong-field “filament” structures. Lastly, magnetic fields grow stronger by turbulence. Field amplification is most effective for low-mass ratio mergers, but mergers with a large impact parameter can increase the magnetic energy more via shearing motions. The amplification of the magnetic field is most effective in between the first two core passages of each cluster merger. After the second core passage, the magnetic energy in this region gradually decreases. In general, the transfer of energy from gas motions to the magnetic field is not significant enough to have a substantial effect on gas mixing and the subsequent increase in entropy, which occurs in cluster cores as a result. In the absence of radiative cooling, this results in an overall decrease of the magnetic field strength in cluster cores. In these regions, the final magnetic field is isotropic, while it can be significantly tangential at larger radii.

Keywords: Galaxy clusters, Magnetic fields, Galaxy mergers
Impact of Cosmic-Ray Feedback on Accretion and Chemistry in Circumstellar Disks. We use the gas-grain chemistry code UCLCHEM to explore the impact of cosmic-ray feedback on the chemistry of circumstellar disks. We model the attenuation and energy losses of the cosmic rays as they propagate outward from the star and also consider ionization due to stellar radiation and radionuclides. For accretion rates typical of young stars of {\dot{M}}* ∼ {10}-9{--}{10}-6 M ⊙ yr-1, we show that cosmic rays accelerated by the stellar accretion shock produce an ionization rate at the disk surface ζ ≳ 10-15 s-1, at least an order of magnitude higher than the ionization rate associated with the Galactic cosmic-ray background. The incident cosmic-ray flux enhances the disk ionization at intermediate to high surface densities (Σ &gt; 10 g cm-2), particularly within 10 au of the star. We find that the dominant ions are C+, S+, and Mg+ in the disk surface layers, while the {{{H}}}3+ ion dominates at surface densities above 1.0 g cm-2. We predict the radii and column densities at which the magnetorotational instability (MRI) is active in T Tauri disks and show that ionization by cosmic-ray feedback extends the MRI-active region toward the disk midplane. However, the MRI is only active at the midplane of a minimum-mass solar nebula disk if cosmic rays propagate diffusively (ζ ∝ r -1) away from the star. The relationship between accretion, which accelerates cosmic rays, the dense accretion columns, which attenuate cosmic rays, and the MRI, which facilitates accretion, creates a cosmic-ray feedback loop that mediates accretion and may produce variable luminosity.

Keywords: Astrochemistry, Protoplanetary disks, Circumstellar disks, Magnetic fields, Cosmic rays