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<jats:title>Abstract</jats:title> <jats:p>The sunspots have been observed since 1610, and their group numbers have been used for evaluating the amplitude of solar activity. Daniel Mögling recorded his sunspot observations for more than 100 days in 1626–1629 and formed a significant data set of sunspot records before the Maunder Minimum. Here we have analyzed his original manuscripts in the Universitäts- und Landesbibliothek Darmstadt to review Mögling’s personal profile and observational instruments and derived the number and positions of the recorded sunspot groups. In his manuscript, we have identified 134 days with an exact sunspot group number and 3 days of additional descriptions. Our analyses have completely revised the observational dates and group numbers, added 19 days of hitherto overlooked observations, and removed 8 days of misinterpreted observations. We have also revisited the sunspot observations of Schickard and Hortensius and revised their data. These results have been compared with the contemporary observations. Moreover, we have derived the sunspot positions from his sunspot drawings and located them at 2°–23° in heliographic latitude in both solar hemispheres. Contextualized with contemporary observations, these results indicate their temporal migration to lower heliographic latitudes and emphasize their location in the declining phase of solar cycle −12 in the 1620s. Mögling’s observations were probably conducted using a pinhole and camera obscura, which likely made him underestimate the sunspot group number by ≥33%–52%. This underestimation should be noted upon comparison with modern data sets.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The observed features of the radio source indicate that the waves of solar radio bursts are convoluted with complex propagation effects. In this work, we perform ray-tracing simulations on radio wave transport in the corona and interplanetary region with anisotropic electron density fluctuations. For the first time, the variation of the apparent source size, burst duration, and source position for the fundamental emission and harmonic emission at the frequency of 35 MHz are simulated as a function of the anisotropic parameter <jats:italic>α</jats:italic> and the angular scattering rate coefficient <jats:italic>η</jats:italic> = <jats:italic>ϵ</jats:italic> <jats:sup>2</jats:sup>/<jats:italic>h</jats:italic> <jats:sub>0</jats:sub>, where <jats:italic>ϵ</jats:italic> <jats:sup>2</jats:sup> = 〈<jats:italic>δ</jats:italic> <jats:italic>n</jats:italic> <jats:sup>2</jats:sup>〉/<jats:italic>n</jats:italic> <jats:sup>2</jats:sup> is the density fluctuation level and <jats:italic>h</jats:italic> <jats:sub>0</jats:sub> is its correlation length near the wave excitation site. It is found that isotropic fluctuations produce a much larger decay time than a highly anisotropic fluctuation for fundamental emission. By comparing the observed duration and source size with the simulation results in the parameter space, we can estimate the scattering coefficient and the anisotropic parameter <jats:italic>η</jats:italic> = 8.9 × 10<jats:sup>−5</jats:sup> km<jats:sup>−1</jats:sup> and <jats:italic>α</jats:italic> = 0.719 with a point pulse source assumption. Position offsets due to wave scattering and refraction can produce the co-spatial of the fundamental and harmonic waves in the observation of some type III radio bursts. The visual speed due to the wave propagation effect can reach 1.5<jats:italic>c</jats:italic> for <jats:italic>η</jats:italic> = 2.4 × 10<jats:sup>−4</jats:sup> km<jats:sup>−1</jats:sup> and <jats:italic>α</jats:italic> = 0.2 for the fundamental emission in the sky plane, accompanied with large expansion rate of the source size. The direction of the visual speed is mostly identical to the direction of the offset, thus, for the observation aimed at obtaining the source position, the source centroid at the starting time is closer to the wave excitation site.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Forbidden neon emission lines from small-scale microjets can probe high-energy processes in low-mass young stellar systems. We obtained spatially resolved [Ne <jats:sc>iii</jats:sc>] spectra in the microjets from the classical T Tauri Star Sz 102 using the Hubble Space Telescope Imaging Spectrograph at a spatial resolution of ∼0.″1. The blueshifted and redshifted [Ne <jats:sc>iii</jats:sc>] emission both peak in intensity within ∼0.″1 of the star and gradually decay along the flow outward to ∼0.″24. The spatial distribution and extent of the [Ne <jats:sc>iii</jats:sc>] microjet is consistent with a jet that is ionized close to the base and subsequently recombines on a longer timescale than the flow time. Ca <jats:sc>ii</jats:sc> H and K lines are also detected from the redshifted microjet with a line full-width at half-maximum of ∼170 km s<jats:sup>−1</jats:sup>, consistent with those of other forbidden emission lines, atop a 300 km s<jats:sup>−1</jats:sup> wide stellar component. The launching radius of the Sz 102 jet, inferred from the observed line centroids and the range of inclination angles and stellar masses from the literature, is on the order of ∼0.03 au. The possible proximity of the launching region to the star allows immediate ionization without distance dilution from the circumstellar ionization sources, most likely keV X-ray flares generated by magnetic reconnection events in the star--disk system, to sustain the observed [Ne <jats:sc>iii</jats:sc>] flux.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Major solar eruptions occasionally direct interplanetary coronal mass ejections (ICMEs) to Earth and cause significant geomagnetic storms and low-latitude aurorae. While individual extreme storms are significant threats to modern civilization, storms occasionally appear in sequence, acting synergistically, and cause “perfect storms” on Earth. The stormy interval in 1938 January was one of such cases. Here, we analyze the contemporary records to reveal its time series on their source active regions, solar eruptions, ICMEs, geomagnetic storms, low-latitude aurorae, and cosmic-ray (CR) variations. Geomagnetic records show that three storms occurred successively on January 17/18 (Dcx ≈ −171 nT), January 21/22 (Dcx ≈ −328 nT), and January 25/26 (Dcx ≈ −336 nT). The amplitudes of the CR variations and storm sudden commencements (SSCs) show the impact of the first ICME as the largest (≈6% decrease in CR and 72 nT in SSC) and the ICMEs associated with the storms that followed as more moderate (≈3% decrease in CR and 63 nT in SSC; ≈2% decrease in CR and 63 nT in SSC). Interestingly, a significant solar proton event occurred on January 16/17 and the Cheltenham ionization chamber showed a possible ground-level enhancement. During the first storm, aurorae were less visible at midlatitudes, whereas, during the second and third storms, the equatorward boundaries of the auroral oval were extended down to 40.3° and 40.0° in invariant latitude. This contrast shows that the initial ICME was probably faster, with a higher total magnitude but a smaller southward component.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report on the discovery of a mysterious ultra-steep-spectrum (USS) synchrotron source in the galaxy cluster A2877. We have observed the source with the Murchison Widefield Array at five frequencies across 72–231 MHz and found the source to exhibit strong spectral curvature over this range, as well as the steepest known spectra of a synchrotron cluster source, with a spectral index across the central three frequency bands of <jats:inline-formula> <jats:tex-math> <?CDATA $\alpha =-{5.97}_{-0.48}^{+0.40}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabe384ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. Higher-frequency radio observations, including a deep observation with the Australia Telescope Compact Array, fail to detect any of the extended diffuse emission. The source is approximately 370 kpc wide and bears an uncanny resemblance to a jellyfish with two peaks of emission and long tentacles descending south toward the cluster center. While the “USS Jellyfish” defies easy classification, we here propose that the phenomenon is caused by the reacceleration and compression of multiple aged electron populations from historic active galactic nucleus (AGN) activity, a so-called “radio phoenix,” by an as yet undetected weak cluster-scale mechanism. The USS Jellyfish adds to a growing number of radio phoenix in cool-core clusters with unknown reacceleration mechanisms; as the first example of a polyphoenix, however, this implies that the mechanism is on the scale of the cluster itself. Indeed, we show that in simulations, emission akin to the USS Jellyfish can be produced as a short-lived transient phase in the evolution of multiple interacting AGN remnants when subject to weak external shocks.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We observed the high-mass star-forming region G335.579–0.292 with the Atacama Large Millimeter/submillimeter Array (ALMA) at 226 GHz with an angular resolution of 0.″3 (∼1000 au resolution at the source distance). G335.579–0.292 hosts one of the most massive cores in the Galaxy (G335–MM1). The continuum emission shows that G335–MM1 fragments into at least five sources, while molecular line emission is detected in two of the continuum sources (ALMA1 and ALMA3). We found evidence of large- and small-scale infall in ALMA1 revealed by an inverse P-Cygni profile and the presence of a blueshifted spot at the center of the first moment map of the CH<jats:sub>3</jats:sub>CN emission. In addition, hot gas expansion in the innermost region is unveiled by a redshifted spot in the first moment map of HDCO and (CH<jats:sub>3</jats:sub>)<jats:sub>2</jats:sub>CO (both with <jats:italic>E</jats:italic> <jats:sub> <jats:italic>u</jats:italic> </jats:sub> &gt; 1100 K). Our modeling reveals that this expansion motion originates close to the central source, likely due to reversal of the accretion flow induced by the expansion of the H <jats:sc>ii</jats:sc> region, while infall and rotation motions originate in the outer regions. ALMA3 shows clear signs of rotation, with a rotation axis inclination with respect to the line of sight close to 90°, and a system mass (disk + star) in the range of 10–30 <jats:italic>M</jats:italic> <jats:sub>☉</jats:sub>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present new near-infrared, <jats:italic>JHK</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub>, period–luminosity relations (PLRs) for RR Lyrae variables in the Messier 53 (M53 or NGC 5024) globular cluster. Multi-epoch <jats:italic>JHK</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub> observations, obtained with the WIRCam instrument on the 3.6 m Canada–France–Hawaii Telescope, are used for the first time to estimate precise mean magnitudes for 63 RR Lyrae stars in M53 including 29 fundamental-mode (RRab) and 34 first-overtone mode (RRc) variables. The <jats:italic>JHK</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub>-band PLRs for RR Lyrae stars are best constrained for RRab types with a minimal scatter of 22, 23, and 19 mmag, respectively. The combined sample of RR Lyrae is used to derive the <jats:italic>K</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub>-band PLR, <jats:inline-formula> <jats:tex-math> <?CDATA ${K}_{s}=-2.303(0.063)\mathrm{log}P+15.212(0.016)$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>K</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>s</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:mn>2.303</mml:mn> <mml:mo stretchy="false">(</mml:mo> <mml:mn>0.063</mml:mn> <mml:mo stretchy="false">)</mml:mo> <mml:mi>log</mml:mi> <mml:mi>P</mml:mi> <mml:mo>+</mml:mo> <mml:mn>15.212</mml:mn> <mml:mo stretchy="false">(</mml:mo> <mml:mn>0.016</mml:mn> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabdf48ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, exhibiting a 1<jats:italic>σ</jats:italic> dispersion of only 0.027 mag. Theoretical period–luminosity–metallicity (PLZ) relations are used to predict parallaxes for 400 Galactic RR Lyrae, resulting in a median parallax zero-point offset of −7 ± 3 <jats:italic>μ</jats:italic>as in Gaia Early Data Release 3 (EDR3), which increases to 22 ± 2 <jats:italic>μ</jats:italic>as if the parallax corrections are applied. We also estimate a robust distance modulus, <jats:italic>μ</jats:italic> <jats:sub>M53</jats:sub> = 16.403 ± 0.024 (statistical) ± 0.033 (systematic) mag, to M53 based on theoretical calibrations. Homogeneous and precise mean magnitudes for RR Lyrae in M53 together with similar literature data for M3, M4, M5, and <jats:italic>ω</jats:italic> Cen are used to empirically calibrate a new RR Lyrae <jats:inline-formula> <jats:tex-math> <?CDATA ${\mathrm{PLZ}}_{{K}_{s}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>PLZ</mml:mi> </mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>K</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>s</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabdf48ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> relation, <jats:inline-formula> <jats:tex-math> <?CDATA ${K}_{s}=-0.848(0.007)\,-2.320(0.006)\mathrm{log}P+0.166(0.011)[\mathrm{Fe}/{\rm{H}}]$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>K</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>s</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:mn>0.848</mml:mn> <mml:mo stretchy="false">(</mml:mo> <mml:mn>0.007</mml:mn> <mml:mo stretchy="false">)</mml:mo> <mml:mspace width="0.25em" /> <mml:mo>−</mml:mo> <mml:mn>2.320</mml:mn> <mml:mo stretchy="false">(</mml:mo> <mml:mn>0.006</mml:mn> <mml:mo stretchy="false">)</mml:mo> <mml:mi>log</mml:mi> <mml:mi>P</mml:mi> <mml:mo>+</mml:mo> <mml:mn>0.166</mml:mn> <mml:mo stretchy="false">(</mml:mo> <mml:mn>0.011</mml:mn> <mml:mo stretchy="false">)</mml:mo> <mml:mo stretchy="false">[</mml:mo> <mml:mi>Fe</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> <mml:mo stretchy="false">]</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabdf48ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>, anchored with Gaia EDR3 distances and theoretically predicted relations, and to simultaneously estimate precise RR Lyrae-based distances to these globular clusters.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this paper, we study kink and sausage oscillations in the presence of longitudinal background flow. We study the resonance absorption of kink and sausage modes in the slow continuum, under magnetic pore conditions, in the presence of flow. We determine the dispersion relation, and solve it numerically to find the frequencies and damping rates of the slow kink and sausage surface modes. We also obtain an analytical solution for the damping rate of the slow surface mode in the long wavelength limit. We show that in the presence of plasma flow, resonance absorption can result in strong damping for forward waves, and can be considered as an efficient mechanism to justify the extremely rapid damping of slow surface sausage waves observed in magnetic pores. Moreover, the plasma flow reduces the efficiency of resonance absorption to damp backward waves. With respect to pore conditions, resonance instability is avoided in our model.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The propagating intensity disturbances (PIDs) in plumes are still poorly understood, and their identity (magnetoacoustic waves or flows) remains an open question. We investigate PIDs in five plumes located in the northern polar coronal hole observed during the 2017 total solar eclipse. Three plumes are associated with coronal bright points, jets, and macrospicules at their base (active plumes), and the other two plumes are not (quiet plumes). The electron temperature at the base of the plumes is obtained from the filter ratio of images taken with the X-ray Telescope on board Hinode and the passband ratio around 400 nm from an eclipse instrument, the Diagnostic Coronagraph Experiment. The phase speed (<jats:italic>v</jats:italic> <jats:sub> <jats:italic>r</jats:italic> </jats:sub>), frequency (<jats:italic>ω</jats:italic>), and wavenumber (<jats:italic>k</jats:italic>) of the PIDs in the plumes are obtained by applying a Fourier transformation to the spacetime (<jats:italic>r</jats:italic> − <jats:italic>t</jats:italic> plane) plots in images taken with the Atmospheric Imaging Assembly (AIA) in three different wavelength channels (171, 193, and 211 Å). We found that the PIDs in the higher-temperature AIA channels, 193 and 211 Å, are faster than that of the cooler AIA 171 Å channel. This tendency is more significant for the active plumes than the quiet ones. The observed speed ratio (∼1.3) between the AIA 171 and 193 Å channels is similar to the theoretical value (1.25) of a slow magnetoacoustic wave. Our results support the idea that PIDs in plumes represent a superposition of slow magnetoacoustic waves and plasma outflows that consist of dense cool flows and hot coronal jets.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Star formation in galaxies is a hierarchical process with a wide range of scales, from smaller clusters to larger stellar complexes. Here, we present an ultra-violet imaging study of the nearby flocculent spiral galaxy NGC 7793, observed using the Ultra-Violet Imaging Telescope (UVIT). We find that the disk scale length estimated in Far-UV (2.64 ± 0.16 kpc) is larger than that in Near-UV (2.21 ± 0.21 Kpc) and optical (1.08 Kpc), which supports the inside-out growth scenario of the galaxy disk. The star-forming UV disk is also found to be contained within the extent of H <jats:sc>i</jats:sc> gas, with a column density greater than 10<jats:sup>21</jats:sup> cm<jats:sup>−2</jats:sup>. With the spatial resolution of UVIT (1 pixel ∼ 6.8 pc), we identified 2046 young star-forming clumps in the galaxy with radii between ∼12 and 70 pc, which matches well with the size of giant molecular clouds (GMCs) detected in the galaxy. Around 61% of the regions identified in our study are younger than 20 Myr, which points to a recent enhancement in star formation across the galaxy. We also note that the youngest star-forming regions, with an age of &lt;10 Myr, distinctly trace the flocculent arms of the galaxy. The estimated mass of the clumps covers a range between 10<jats:sup>3</jats:sup> and 10<jats:sup>6</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. We notice a gradient in the mass distribution of identified clumps along the spiral arms. We also study the nuclear star cluster of the galaxy, finding that the stellar populations in the cluster outskirts are younger than the inner part.</jats:p>