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Abstract Minifilament eruptions producing small jets and microflares have mostly been studied based on coronal observations at extreme-ultraviolet and X-ray wavelengths. This study presents chromospheric plasma diagnostics of a quiet-Sun minifilament of size ∼ 2″ × 5″ with a sigmoidal shape and an associated microflare observed on 2021 August 7 17:00 UT using high temporal and spatial resolution spectroscopy from the Fast Imaging Solar Spectrograph (FISS) and high-resolution magnetograms from the Near InfraRed Imaging Spectropolarimeter (NIRIS) installed on the 1.6 m Goode Solar Telescope at Big Bear Solar Observatory. Using FISS Hαand Caii8542 Å line spectra at the time of the minifilament activation we determined a temperature of 8600 K and a nonthermal speed of 7.9 km s⁻¹. During the eruption, the minifilament was no longer visible in the Caii8542 Å line, and only the Hαline spectra were used to find the temperature of the minifilament, which reached 1.2 × 10⁴K and decreased afterward. We estimated thermal energy of 3.6 × 10²⁴erg from the maximum temperature and kinetic energy of 2.6 × 10²⁴erg from the rising speed (18 km s⁻¹) of the minifilament. From the NIRIS magnetograms we found small-scale flux emergence and cancellation coincident with the minifilament eruption, and the magnetic energy change across the conjugate footpoints reaches 7.2 × 10²⁵erg. Such spectroscopic diagnostics of the chromospheric minifilament complement earlier studies of minifilament eruptions made using coronal images. 

Abstract Spicules, the smallest observable jetlike dynamic features ubiquitous in the chromosphere, are supposedly an important potential source for small-scale solar wind transients, with supporting evidence yet needed. We studied the high-resolution Hαimages (0.″10) and magnetograms (0.″29) from the Big Bear Solar Observatory to find that spicules are an ideal candidate for the solar wind magnetic switchbacks detected by the Parker Solar Probe (PSP). It is not that spicules are a miniature of coronal jets, but that they have unique properties not found in other solar candidates in explaining solar origin of switchbacks. (1) The spicules under this study originate from filigrees, all in a single magnetic polarity. Since filigrees are known as footpoints of open fields, the spicule guiding field lines can form a unipolar funnel, which is needed to create an SB patch, a group of field lines that switch from one common base polarity to the other polarity. (2) The spicules come in a cluster lined up along a supergranulation boundary, and the simulated waiting times from their spatial intervals exhibit a number distribution continuously decreasing from a few seconds to ∼30 minutes, similar to that of switchbacks. (3) From a time–distance map for spicules, we estimate their occurrence rate as 0.55 spicules Mm⁻²s⁻¹, which is sufficiently high for detection by PSP. In addition, the dissimilarity of spicules with coronal jets, including the absence of base brightening and low correlation with EUV emission, is briefly discussed. 

Abstract We used 29 high-resolution line-of-sight magnetograms acquired with the Goode Solar Telescope (GST) in a quiet-Sun area to extrapolate a series of potential field configurations and study their time variations. The study showed that there are regions that consistently exhibit changes in loop connectivity, whereas other vast areas do not show such changes. Analysis of the topological features of the potential fields indicates that the photospheric footprint of the separatrix between open- and closed-loop systems closely matches the roots of rapid blue- and redshifted excursions, which are disk counterparts of type II spicules. There is a tendency for the footpoints of the observed H_αfeatures to be cospatial with the footpoints of the loops that most frequently change their connectivity, while the area occupied by the open fields that did not show any significant and persistent connectivity changes is void of prominent jet and spicular activity. We also detected and tracked magnetic elements using the Southwest Automatic Magnetic Identification Suite and GST magnetograms, which allowed us to construct artificial magnetograms and calculate the corresponding potential field configurations. Analysis of the artificial data showed tendencies similar to those found for the observed data. The present study suggests that a significant amount of chromospheric activity observed in the far wings of the H_αspectral line may be generated by reconnecting closed-loop systems and canopy fields consisting of “open” field lines. 

A series of dramatic oceanic and atmospheric events occurred in the immediate aftermath of the Marinoan “snowball Earth” meltdown ∼635 My ago. However, at the 10- to 100-ky timescale, the order, rate, duration, and causal-feedback relationships of these individual events remain nebulous. Nonetheless, rapid swings in regional marine sulfate concentrations are predicted to have occurred in the aftermath of a snowball Earth, due to the nonlinear responses of its two major controlling fluxes: oxidative weathering on the continents and pyrite burial in marine sediments. Here, through the application of multiple isotope systems on various carbon and sulfur compounds, we determined extremely 13 C-depleted calcite cements in the basal Ediacaran in South China to be the result of microbial sulfate reduction coupled to anaerobic oxidation of methane, which indicates an interval of high sulfate concentrations in some part of the postmeltdown ocean. Regional chemostratigraphy places the 13 C-depleted cements at the equivalent of the earliest Ediacaran 17 O-depletion episode, thus confining the timing of this peak in sulfate concentrations within ∼50 ky since the onset of the deglaciation. The dearth of similarly 13 C-depleted cements in other Proterozoic successions implies that the earliest Ediacaran peak in marine sulfate concentration is a regional and likely transient event. 

Abstract In this study, we analyze high-spatial-resolution (0.″24) magnetograms and high-spatial-resolution (0.″10) Hαoff-band (± 0.8 Å) images taken by the 1.6 m Goode Solar Telescope to investigate the magnetic properties associated with small-scale ejections in a coronal hole boundary region from a statistical perspective. With one and a half hours of optical observations under excellent seeing, we focus on the magnetic structure and evolution by tracking the magnetic features with the Southwest Automatic Magnetic Identification Suite (SWAMIS). The magnetic field at the studied coronal hole boundary is dominated by negative polarity with flux cancellations at the edges of the negative unipolar cluster. In a total of 1250 SWAMIS-detected magnetic cancellation events, ∼39% are located inside the coronal hole with an average flux cancellation rate of 2.0 × 10¹⁸Mx Mm⁻²hr⁻¹, and ∼49% are located outside the coronal hole with an average flux cancellation rate of 8.8 × 10¹⁷Mx Mm⁻²hr⁻¹. We estimated that the magnetic energy released due to flux cancellation inside the coronal hole is six times more than that outside the coronal hole. Flux cancellation accounts for ∼9.5% of the total disappearance of magnetic flux. Other forms of its disappearance are mainly due to fragmentation of unipolar clusters or merging with elements of the same polarity. We also observed a number of significant small-scale ejections associated with magnetic cancellations at the coronal hole boundary that have corresponding EUV brightenings.