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<jats:title>Abstract</jats:title> <jats:p>Coronal mass ejections (CMEs) and coronal jets are two types of common solar eruptive phenomena, which often independently happen at different spatial scales. In this work, we present a stereoscopic observation of a large-scale CME flux rope arising from an unwinding blowout jet in a multipolar complex magnetic system. Based on a multiband observational analysis, we find that this whole event starts with a small filament whose eruption occurs at a coronal geyser site after a series of homologous jets. Aided by magnetic field extrapolations, it reveals that the coronal geyser site forms above an elongate opposite-polarity interface, where the emergence-driven photospheric flux cancellation and repetitive reconnection are responsible for those preceding recurrent jets and also contribute to the ultimate filament destabilization. By interacting with overlying fields, the erupting filament breaks one of its legs, and results in an unwinding blowout jet. Our estimation suggests that around 1.4–2.0 turns of twist release in its jet spire. This prominent twist transport in the jet spire rapidly creates a newborn larger-scale flux rope from the jet base to a remote site. Soon after its formation, this large-scale flux rope erupts toward the outer coronae causing an Earth-directed CME. In its source region, two sets of distinct postflare loops form in succession, indicating this eruption involves two stages of flare magnetic reconnection. This work not only reveals a real magnetic coupling process between different eruptive activities but provides a new hint for understanding for the creation of large-scale CME flux ropes during the solar eruption.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>High-resolution very long baseline interferometry (VLBI) radio observations have resolved the detailed emission structures of active galactic nucleus jets. General relativistic magnetohydrodynamic (GRMHD) simulations have improved the understanding of jet production physics, although theoretical studies still have difficulty constraining the origin and distribution of jetted matter. We construct a new steady, axisymmetric GRMHD jet model to obtain approximate solutions of black hole (BH) magnetospheres, and examine the matter density distribution of jets. By assuming fixed poloidal magnetic field shapes that mimic force-free analytic solutions and GRMHD simulation results and assuming constant poloidal velocity at the separation surface, which divides the inflow and outflow, we numerically solve the force balance between the field lines at the separation surface and analytically solve the distributions of matter velocity and density along the field lines. We find that the densities at the separation surface in our parabolic field models roughly follow <jats:inline-formula> <jats:tex-math> <?CDATA $\propto {r}_{\mathrm{ss}}^{-2}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabe61bieqn1.gif" xlink:type="simple" /> </jats:inline-formula> in the far zone from the BH, where <jats:italic>r</jats:italic> <jats:sub>ss</jats:sub> is the radius of the separation surface. When the BH spin is larger or the velocity at the separation surface is smaller, the density at the separation surface becomes concentrated closer to the jet edge. Our semianalytic model, combined with radiative transfer calculations, may help us interpret the high-resolution VLBI observations and understand the origin of jetted matter.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the first detailed polarimetric studies of Cygnus A at 230 GHz with the Submillimeter Array (SMA) to constrain the mass accretion rate onto its supermassive black hole. We detected the polarized emission associated with the core at a fractional polarization of <jats:inline-formula> <jats:tex-math> <?CDATA $0.73\pm 0.15 \% $?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabd17bieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. This low fractional polarization suggests that the polarized emission is highly depolarized. One of the possible explanations is due to a significant variance in the Faraday rotation measure within the synthesized beam. By assuming the Faraday depolarization caused by inhomogeneous column density of the magnetized plasma associated with the surrounding radiatively-inefficient accretion flow within the SMA beam, we derived the constraint on the mass accretion rate to be larger than 0.15 <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{\odot }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabd17bieqn2.gif" xlink:type="simple" /> </jats:inline-formula> yr<jats:sup>−1</jats:sup> at the Bondi radius. The derived constraint indicates that an adiabatic inflow–outflow solution or an advection-dominated accretion flow should be preferable as the accretion flow model in order to explain the jet power of Cygnus A.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Extreme-ultraviolet Variability Experiment (EVE) onboard the Solar Dynamics Observatory detects the solar EUV spectra with high temporal cadence and spectral resolution. The wavelength shifts of emission lines provide key information of the dynamics of the Sun. However, some of EVE spectral observations are influenced by the non-uniformly distributed irradiance on the Sun, which may prevent us from correctly understanding the physical processes happening in the solar corona. Here, based on the only published on-orbit calibration data of EVE He <jats:sc>II</jats:sc> 30.38 nm line on 2011 January 27, we develop a method to correct the He <jats:sc>II</jats:sc> 30.38 nm line by using AIA 304 imaging data. This correction method is then applied to EVE He <jats:sc>II</jats:sc> 30.38 nm data from 2010 October 29 to 2011 March 3 to study the Doppler oscillations of the solar He <jats:sc>II</jats:sc> 30.38 nm line, in which we show that the half-month periodic Doppler oscillation is caused by non-uniformly distributed irradiance mainly due to the presence of active regions. Other EVE coronal lines also present similar Doppler oscillations, suggesting that an appropriate correction must be implemented before interpreting the oscillation phenomena appearing in these lines.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Probing magnetic fields in the interstellar medium (ISM) is notoriously challenging. Motivated by the modern theories of magnetohydrodynamic (MHD) turbulence and turbulence anisotropy, we introduce the Structure Function Analysis (SFA) as a new approach to measure the magnetic-field orientation and estimate the magnetization. We analyze the statistics of turbulent velocities in three-dimensional compressible MHD simulations through the second-order structure functions in both local and global reference frames. In the sub-Alfvénic turbulence with the magnetic energy larger than the turbulent energy, the SFA of turbulent velocities measured in the directions perpendicular and parallel to the magnetic field can be significantly different. Their ratio has a power-law dependence on the Alfvén Mach number <jats:italic>M</jats:italic> <jats:sub>A</jats:sub>, which is inversely proportional to the magnetic-field strength. We demonstrate that the anisotropic structure functions of turbulent velocities can be used to estimate both the orientation and strength of magnetic fields. With turbulent velocities measured using different tracers, our approach can be generally applied to probing the magnetic fields in the multiphase ISM.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>OH megamasers (OHMs) are rare, luminous masers found in gas-rich major galaxy mergers. In untargeted neutral hydrogen (H <jats:sc>i</jats:sc>) emission-line surveys, spectroscopic redshifts are necessary to differentiate the <jats:italic>λ</jats:italic> <jats:sub>rest</jats:sub> = 18 cm masing lines produced by OHMs from H <jats:sc>i</jats:sc> 21 cm lines. Next-generation H <jats:sc>i</jats:sc> surveys will detect an unprecedented number of galaxies, most of which will not have spectroscopic redshifts. We present predictions for the numbers of OHMs that will be detected and the potential “contamination” they will impose on H <jats:sc>i</jats:sc> surveys. We examine the Looking at the Distant Universe with the MeerKAT Array (LADUMA), a single-pointing deep-field survey reaching redshift <jats:italic>z</jats:italic> <jats:sub>H <jats:sc>I</jats:sc> </jats:sub> = 1.45, as well as potential future surveys with the Square Kilometre Array (SKA) that would observe large portions of the sky out to redshift <jats:italic>z</jats:italic> <jats:sub>H <jats:sc>I</jats:sc> </jats:sub> = 1.37. We predict that LADUMA will potentially double the number of known OHMs, creating an expected contamination of 1.0% of the survey’s H <jats:sc>i</jats:sc> sample. Future SKA H <jats:sc>i</jats:sc> surveys are expected to see up to 7.2% OH contamination. To mitigate this contamination, we present methods to distinguish H <jats:sc>i</jats:sc> and OHM host populations without spectroscopic redshifts using near- to mid-IR photometry and a <jats:italic>k</jats:italic>-Nearest Neighbors algorithm. Using our methods, nearly 99% of OHMs out to redshift <jats:italic>z</jats:italic> <jats:sub>OH</jats:sub> ∼ 1.0 can be correctly identified. At redshifts out to <jats:italic>z</jats:italic> <jats:sub>OH</jats:sub> ∼ 2.0, 97% of OHMs can be identified. The discovery of these high-redshift OHMs will be valuable for understanding the connection between extreme star formation and galaxy evolution.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this study, we investigate analytically the generation of mass flux due to a torsional Alfvén pulse. We derive that the presence of torsional Alfvén waves, which have been observed in, e.g., photospheric magnetic bright points (MBPs), can result in vertical plasma motions. The formation of this mass flux may even be a viable contribution to the generation of chromospheric mass transport, playing potential roles in the form of localized lower solar atmospheric jets. This relationship is studied using a flux tube model, with the waves introduced at the lower boundary of the tube as a magnetic shear perturbation. Due to the nature of MBPs we simplify the model by using the zero-beta approximation for the plasma inside the tube. The analytical results are demonstrated by an example of the type of Alfvén wave perturbation that one might expect to observe, and comparison is made with properties of spicules known from observations. We find that field-aligned plasma flux is formed nonlinearly as a result of the Lorentz force generated by the perturbations, and could be consistent with jet formation, although the current model is not intended to determine the entire evolution of a jet. Critical discussion of the model follows, including suggestions for improvements and for high-resolution proposed observations in order to constrain the driving magnetic and velocity shear.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The gas-to-dust ratio of reddened stars in the Milky Way (MW), the Magellanic Clouds, and in general, is usually expressed as a linear relation between the hydrogen column density, <jats:italic>N</jats:italic>(H), and the reddening, <jats:italic>E</jats:italic>(<jats:italic>B</jats:italic> − <jats:italic>V</jats:italic>), or extinction in the <jats:italic>V-</jats:italic>band (<jats:italic>A</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub>). If the extinction curve were truly universal, the strength of the relationship and the linearity would naturally be maintained for extinction at any wavelength, as well as for <jats:italic>N</jats:italic>(H) versus <jats:italic>E</jats:italic>(<jats:italic>B</jats:italic> − <jats:italic>V</jats:italic>). However, extinction curves vary within the MW, and there is no reason, except by chance, why either <jats:italic>E</jats:italic>(<jats:italic>B</jats:italic> − <jats:italic>V</jats:italic>) or <jats:italic>A</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> would be the most physical measure of dust column density. In this paper, we utilize for the first time full extinction curves to 41 MW sightlines, finding that the scatter between <jats:italic>N</jats:italic>(H) and extinction is minimized—and the relation becomes linear—for extinction at 2900 ± 160 Å. Scatter and nonlinearity increase at longer wavelengths, and are especially large for near-IR extinction. We conclude that near-UV extinction is a superior measure of the dust column density for MW dust. We provide new, nonlinear gas-to-dust relations for various dust tracers. We also find that the very large discrepancy between MW and SMC gas-to-dust ratios of 0.9 dex in <jats:italic>N</jats:italic>(H)/<jats:italic>E</jats:italic>(<jats:italic>B</jats:italic> − <jats:italic>V</jats:italic>) is reduced to 0.7 dex for far-UV extinction, which matches the difference in cosmic abundances of carbon between the two galaxies, and therefore confirms that <jats:italic>N</jats:italic>(C) is the preferred measure for gas in the gas-to-dust ratio, even though it may not be a convenient one.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Internetwork (IN) magnetic fields are highly dynamic, short-lived magnetic structures that populate the interior of supergranular cells. Since they emerge all over the Sun, these small-scale fields bring a substantial amount of flux, and therefore energy, to the solar surface. Because of this, IN fields are crucial for understanding the quiet Sun (QS) magnetism. However, they are weak and produce very small polarization signals, which is the reason why their properties and impact on the energetics and dynamics of the solar atmosphere are poorly known. Here we use coordinated, high-resolution, multiwavelength observations obtained with the Swedish 1 m Solar Telescope and the Interface Region Imaging Spectrograph (IRIS) to follow the evolution of IN magnetic loops as they emerge into the photosphere and reach the chromosphere and transition region. We studied in this paper three flux emergence events having total unsigned magnetic fluxes of 1.9 × 10<jats:sup>18</jats:sup>, 2.5 × 10<jats:sup>18</jats:sup>, and 5.3 × 10<jats:sup>18</jats:sup> Mx. The footpoints of the emerging IN bipoles are clearly seen to appear in the photosphere and to rise up through the solar atmosphere, as observed in Fe <jats:sc>i</jats:sc> 6173 Å and Mg <jats:sc>i</jats:sc> b<jats:sub>2</jats:sub> 5173 Å magnetograms, respectively. For the first time, our polarimetric measurements taken in the chromospheric Ca <jats:sc>ii</jats:sc> 8542 Å line provide direct observational evidence that IN fields are capable of reaching the chromosphere. Moreover, using IRIS data, we study the effects of these weak fields on the heating of the chromosphere and transition region.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present F<jats:sc>or</jats:sc>SE (Foreground Scale Extender), a novel Python package that aims to overcome the current limitations in the simulation of diffuse Galactic radiation, in the context of cosmic microwave background (CMB) experiments. F<jats:sc>or</jats:sc>SE exploits the ability of generative adversarial neural networks (GANs) to learn and reproduce complex features present in a set of images, with the goal of simulating realistic and non-Gaussian foreground radiation at subdegree angular scales. This is of great importance in order to estimate the foreground contamination to lensing reconstruction, delensing, and primordial <jats:italic>B</jats:italic>-modes for future CMB experiments. We applied this algorithm to Galactic thermal dust emission in both total intensity and polarization. Our results show how F<jats:sc>or</jats:sc>SE is able to generate small-scale features (at 12′) having as input the large-scale ones (80′). The injected structures have statistical properties, evaluated by means of the Minkowski functionals, in good agreement with those of the real sky and which show the correct amplitude scaling as a function of the angular dimension. The obtained thermal dust Stokes <jats:italic>Q</jats:italic> and <jats:italic>U</jats:italic> full-sky maps as well as the F<jats:sc>or</jats:sc>SE package are publicly available for download.</jats:p>