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<jats:title>Abstract</jats:title> <jats:p>Oscillatory reconnection can manifest through the interaction between the ubiquitous MHD waves and omnipresent null points in the solar atmosphere and is characterized by an inherent periodicity. In the current study, we focus on the relationship between the period of oscillatory reconnection and the strength of the wave pulse initially perturbing the null point, in a hot coronal plasma. We use the PLUTO code to solve the fully compressive, resistive MHD equations for a 2D magnetic X-point. Using wave pulses with a wide range of amplitudes, we perform a parameter study to obtain values for the period, considering the presence and absence of anisotropic thermal conduction separately. In both cases, we find that the resulting period is independent of the strength of the initial perturbation. The addition of anisotropic thermal conduction only leads to an increase in the mean value for the period, in agreement with our previous study. We also consider a different type of initial driver and we obtain an oscillation period matching the independent trend previously mentioned. Thus, we report for the first time on the independence between the type and strength of the initializing wave pulse and the resulting period of oscillatory reconnection in a hot coronal plasma. This makes oscillatory reconnection a promising mechanism to be used within the context of coronal seismology.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Previous <jats:italic>Ku</jats:italic>-band (15 GHz) imaging with data obtained from the Very Long Baseline Array (VLBA) had shown two compact, subparsec components at the location of a presumed kiloparsec-scale radio core in Seyfert galaxy NGC 7674. It was then presumed that these two unresolved and compact components were dual radio cores corresponding to two supermassive black holes (SMBHs) accreting surrounding gas and launching radio-bright relativistic jets. However, utilizing the original VLBA data set used to claim the detection of a binary SMBH, in addition to later multiepoch/multifrequency data sets obtained from both the VLBA and the European very long baseline interferometry (VLBI) network, we find no evidence to support the presence of a binary SMBH. We place stringent upper limits to the flux densities of any subparsec-scale radio cores that are at least an order of magnitude lower than the original VLBI radio-core detections, directly challenging the original binary SMBH detection claim. With this in mind, we discuss the possible reasons for the nondetection of any VLBI radio cores in our imaging, the possibility of a binary SMBH still residing in NGC 7674, and the prospect of future observations shedding further light on the true nature of this active galactic nucleus.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Understanding the collisional behavior of dust aggregates consisting of submicron-sized grains is essential to unveiling how planetesimals formed in protoplanetary disks. It is known that the collisional behavior of individual dust particles strongly depends on the strength of viscous dissipation force; however, impacts of viscous dissipation on the collisional behavior of dust aggregates have not been studied in detail, especially for the cases of oblique collisions. Here we investigated the impacts of viscous dissipation on the collisional behavior of dust aggregates. We performed numerical simulations of collisions between two equal-mass dust aggregates with various collision velocities and impact parameters. We also changed the strength of viscous dissipation force systematically. We found that the threshold collision velocity for the fragmentation of dust aggregates barely depends on the strength of viscous dissipation force when we consider oblique collisions. In contrast, the size distribution of fragments changes significantly when the viscous dissipation force is considered. We obtained the empirical fitting formulae for the size distribution of fragments for the case of strong dissipation, which would be useful to study the evolution of size and spatial distributions of dust aggregates in protoplanetary disks.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the Tenerife Inversion Code (TIC), which has been developed to infer the magnetic and plasma properties of the solar chromosphere and transition region via full Stokes inversion of polarized spectral lines. The code is based on the HanleRT forward engine, which takes into account many of the physical mechanisms that are critical for a proper modeling of the Stokes profiles of spectral lines originating in the tenuous and highly dynamic plasmas of the chromosphere and transition region: the scattering polarization produced by quantum level imbalance and interference (atomic polarization), the effects of frequency coherence in polarized resonance scattering (partial redistribution), and the impact of arbitrary magnetic fields on the atomic polarization and the radiation field. We present first results of atmospheric and magnetic inversions, and discuss future developments for the project.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We studied the propagation of ultra-high-energy cosmic rays in extragalactic magnetic fields (EGMFs). We report on the effect of the EGMF on the large-scale anisotropy signal measured at Earth. We show how a spurious dipolar and quadrupolar signal can be generated by the EGMF even if the source distribution is isotropic.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Since its launch, the Alpha Magnetic Spectrometer-02 (AMS-02) has delivered outstanding quality measurements of the spectra of cosmic-ray (CR) species, <jats:inline-formula> <jats:tex-math> <?CDATA $\bar{p}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>p</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac7443ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, <jats:italic>e</jats:italic> <jats:sup>±</jats:sup>, and nuclei (H–Si, Fe), which resulted in a number of breakthroughs. The most recent AMS-02 result is the measurement of the spectra of CR sodium and aluminum up to ∼2 TV. Given their low solar system abundances, a significant fraction of each element is produced in fragmentations of heavier species, predominantly Ne, Mg, and Si. In this paper, we use precise measurements of the sodium and aluminum spectra by AMS-02 together with ACE-CRIS and Voyager 1 data to test their origin. We show that the sodium spectrum agrees well with the predictions made with the <jats:sc>GalProp</jats:sc>-<jats:sc>HelMod</jats:sc> framework, while the aluminum spectrum shows a significant excess in the rigidity range from 2–7 GV. In this context, we discuss the origin of other low-energy excesses in Li, F, and Fe found earlier. The observed excesses in Li, F, and Al appear to be consistent with the local Wolf-Rayet stars hypothesis, invoked to reproduce anomalous <jats:sup>22</jats:sup>Ne/<jats:sup>20</jats:sup>Ne, <jats:sup>12</jats:sup>C/<jats:sup>16</jats:sup>O, and <jats:sup>58</jats:sup>Fe/<jats:sup>56</jats:sup>Fe ratios in CRs, while excess in Fe is likely connected with a past supernova activity in the solar neighborhood. We also provide updated local interstellar spectra (LIS) of sodium and aluminum in the rigidity range from a few megavolts to ∼2 TV. Our calculations employ the self-consistent <jats:sc>GalProp</jats:sc>-<jats:sc>HelMod</jats:sc> framework, which has proved to be a reliable tool in deriving the LIS of CR <jats:inline-formula> <jats:tex-math> <?CDATA $\bar{p}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>p</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac7443ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>, <jats:italic>e</jats:italic> <jats:sup>−</jats:sup>, and nuclei <jats:italic>Z</jats:italic> ≤ 28.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We performed 2D magnetohydrodynamical numerical experiments to study the response of the coronal magnetic configuration to the newly emerging magnetic flux. The configuration includes an electric-current-carrying flux rope modeling the prominence floating in the corona and the background magnetic field produced by two separated magnetic dipoles embedded in the photosphere. Parameters for one dipole are fixed in space and time to model the quiet background, and those for another one are time dependent to model the new flux. These numerical experiments duplicate important results of the analytic solution but also reveal new results. Unlike previous works, the configuration here possesses no symmetry, and the flux rope could move in any direction. The non-force-free environment causes the deviation of the flux rope equilibrium in the experiments from that determined in the analytic solution. As the flux rope radius decreases, the equilibrium could be found, and it evolves quasi-statically until the flux rope reaches the critical location at which the catastrophe occurs. As the radius increases, no equilibrium exists at all. During the catastrophe, two current sheets form in different ways. One forms as the surrounding closed magnetic field is stretched by the catastrophe, and another one forms as the flux rope squeezes the magnetic field nearby. Although reconnection happens in both the current sheets, it erases the first one quickly and enhances the second simultaneously. These results indicate the occurrence of the catastrophe in asymmetric and non-force-free environment, and the non-radial motion of the flux rope following the catastrophe.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We consider the acceleration of charged particles in relativistic shearing flows, with Lorentz factor up to Γ<jats:sub>0</jats:sub> ∼ 20. We present numerical solutions to the particle transport equation and compare these with results from analytical calculations. We show that in the highly relativistic limit the particle energy spectrum that results from acceleration approaches a power law, <jats:inline-formula> <jats:tex-math> <?CDATA $N(E)\propto {E}^{-\tilde{q}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>N</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi>E</mml:mi> <mml:mo stretchy="false">)</mml:mo> <mml:mo>∝</mml:mo> <mml:msup> <mml:mrow> <mml:mi>E</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mover accent="true"> <mml:mrow> <mml:mi>q</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>˜</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac729cieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, with a universal value <jats:inline-formula> <jats:tex-math> <?CDATA $\tilde{q}=(1+\alpha )$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>q</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>˜</mml:mo> </mml:mrow> </mml:mover> <mml:mo>=</mml:mo> <mml:mo stretchy="false">(</mml:mo> <mml:mn>1</mml:mn> <mml:mo>+</mml:mo> <mml:mi>α</mml:mi> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac729cieqn2.gif" xlink:type="simple" /> </jats:inline-formula> for the slope of this power law, where <jats:italic>α</jats:italic> parameterizes the power-law momentum dependence of the particle mean free path. At mildly relativistic flow speeds, the energy spectrum becomes softer and sensitive to the underlying flow profile. We explore different flow examples, including Gaussian and power-law-type velocity profiles, showing that the latter yield comparatively harder spectra, producing <jats:inline-formula> <jats:tex-math> <?CDATA $\tilde{q}\simeq 2$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>q</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>˜</mml:mo> </mml:mrow> </mml:mover> <mml:mo>≃</mml:mo> <mml:mn>2</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac729cieqn3.gif" xlink:type="simple" /> </jats:inline-formula> for Γ<jats:sub>0</jats:sub> ≃ 3 and Kolmogorov turbulence. We provide a comparison with a simplified leaky-box approach and derive an approximate relation for estimating the spectral index as a function of the maximum shear flow speed. These results are of relevance for jetted, high-energy astrophysical sources such as active galactic nuclei, since shear acceleration is a promising mechanism for the acceleration of charged particles to relativistic energies and is likely to contribute to the high-energy radiation observed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the statistical redshift distribution of a large sample of low-surface-brightness (LSB) galaxies identified in the first 200 deg<jats:sup>2</jats:sup> of the Hyper Suprime-Cam Strategic Survey Program. Through cross-correlation with the NASA–SDSS Atlas, we find that the majority of objects lie within <jats:italic>z</jats:italic> &lt; 0.15 or ∼500 Mpc, yielding a mass range of <jats:italic>M</jats:italic> <jats:sub>*</jats:sub> ≈ 10<jats:sup>7</jats:sup>−10<jats:sup>9</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> and a size range of <jats:italic>r</jats:italic> <jats:sub>eff,<jats:italic>g</jats:italic> </jats:sub> ≈ 1−8 kpc. We find a peak in the distance distribution within 100 Mpc, corresponding mostly to ∼10<jats:sup>7</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> galaxies that fall on the known mass–size relation. There is also a tail in the redshift distribution out to <jats:italic>z</jats:italic> ≈ 0.15, comprising more massive (<jats:italic>M</jats:italic> <jats:sub>*</jats:sub> = 10<jats:sup>8</jats:sup> − 10<jats:sup>9</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) galaxies at the larger end of our size range. We see tentative evidence that at the higher-mass end (<jats:italic>M</jats:italic> <jats:sub>*</jats:sub> &gt; 10<jats:sup>8</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>), the LSB galaxies do not form a smooth extension of the mass–size relation of higher-surface-brightness galaxies, perhaps suggesting that the LSB galaxy population is distinct in its formation path.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We investigated the observational properties of Triangulum-Andromeda (TriAnd), Monoceros Ring (MRi), and Anti-Center Stream (ACS) in the anticenter region using K giants, M giants, and RGB stars from LAMOST and SDSS survey. The Friends of Friends algorithm was applied to select member stars of these structures. We found a new spur of TriAnd at <jats:italic>l</jats:italic> ∼ 133° based on member stars selected in this work and compiled from the literature. The distributions of radial velocity and proper motion of its member stars indicate that TriAnd is gradually moving away from the Sun. The comparisons of [Fe/H] and [<jats:italic>α</jats:italic>/Fe] between TriAnd and thick-disk/halo stars reveal that TriAnd is likely to originate from the thick disk. MRi and ACS are adjacent in space with a boundary around latitude 30°, and there is no significant difference between the two structures in velocity, proper motions, and orbits. We suggested that MRi and ACS probably have a common origin. We made projections of the four structures in three-dimensional space for the exploration of the movements between the Sagittarius (Sgr) stellar stream and MRi, and found that a new spur was formed by the Sgr stream members in the velocity distribution as it passed through the MRi region.</jats:p>