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Abstract We present observations of and a magnetic reconnection scenario for a twin pair of “atypical flares” that occurred on 2022 April 22 in a quadrupolar magnetic configuration formed by two active regions. The spatiotemporal evolution of the two flares is examined using images from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory and from the ground-based Multi-Application Solar Telescope in Udaipur, India. Characteristic of atypical flares and indicative of slipping reconnection, the ribbons of each of our atypical flares: (1) do not spread apart; and (2) grow longer by the sequential brightening of new flare kernels. The two atypical flares are homologous and plausibly have homologous triggers. There are four additional pairs of flare ribbons, each from a different flaring event releasing much less energy than the atypical flares. Two of these four pairs are each made by a precursor, each possibly triggering one of the two atypical flares. The remaining two pairs accompany a filament’s activation, occurring twice within the span of the two atypical flares. Using a nonlinear force-free-field extrapolation model, we approximate the coronal magnetic field and find two quasi-separatrix layers (QSLs) that are nearly rooted in the flare ribbons of the atypical flares. The observations and the extrapolated field together suggest a scenario in which the nearly simultaneous occurrence of many reconnections between magnetic field lines crossing each other at small angles (slipping reconnection)withineach of the two QSLs makes the observed pair of atypical flares. 

Abstract We analyzed the inverse Evershed flow (IEF) around a sunspot (NOAA 13131) using line scan observations in the Fei6173 Å and Caii8542 Å spectral lines, complemented with data products from the Solar Dynamics Observatory's Helioseismic and Magnetic Imager. Line-of-sight (LOS) velocities were obtained for different bisector levels in both spectral lines. Additionally, the Caii8542 Å spectra were inverted using the Non-LTE Inversion COde using the Lorien Engine (or NICOLE) to retrieve the temperature and velocity stratification over different layers of the lower solar atmosphere. The IEF evolved dynamically in time and with height in the solar atmosphere. The flow speed associated with the IEF channels was on the order of 8 km s⁻¹in the upper chromosphere, which decreased in the lower layers of the atmosphere. The flow was traced to the lower chromosphere in LOS velocity maps and the upper photosphere in intensity images. The temperature enhancements associated with the IEF were up to 300 K at logτ≈ −2 and 800 K at logτ≈ −6 near the end point of one channel. The overall appearance of the flow along the IEF channels seems consistent with a siphon flow model. We investigated the association of the IEF with the photospheric Evershed flow, but no obvious connection was found in our analysis. We also analyzed the effect of the IEF on moving magnetic features (MMF) selected near and away from IEF channels. MMFs moved radially outward with velocities in the 0.2–1 km s⁻¹range, with no apparent association with the IEF. 

Abstract Sunspot light bridges (LBs) exhibit a wide range of short-lived phenomena in the chromosphere and transition region. In contrast, we use here data from the Multi-Application Solar Telescope (MAST), the Interface Region Imaging Spectrograph (IRIS), Hinode, the Atmospheric Imaging Assembly (AIA), and the Helioseismic and Magnetic Imager (HMI) to analyze the sustained heating over days in an LB in a regular sunspot. Chromospheric temperatures were retrieved from the MAST Caiiand IRIS Mgiilines by nonlocal thermodynamic equilibrium inversions. Line widths, Doppler shifts, and intensities were derived from the IRIS lines using Gaussian fits. Coronal temperatures were estimated through the differential emission measure, while the coronal magnetic field was obtained from an extrapolation of the HMI vector field. At the photosphere, the LB exhibits a granular morphology with field strengths of about 400 G and no significant electric currents. The sunspot does not fragment, and the LB remains stable for several days. The chromospheric temperature, IRIS line intensities and widths, and AIA 171 and 211 Å intensities are all enhanced in the LB with temperatures from 8000 K to 2.5 MK. Photospheric plasma motions remain small, while the chromosphere and transition region indicate predominantly redshifts of 5–20 km s⁻¹with occasional supersonic downflows exceeding 100 km s⁻¹. The excess thermal energy over the LB is about 3.2 × 10²⁶erg and matches the radiative losses. It could be supplied by magnetic flux loss of the sunspot (7.5 × 10²⁷erg), kinetic energy from the increase in the LB width (4 × 10²⁸erg), or freefall of mass along the coronal loops (6.3 × 10²⁶erg). 

This white paper is on the HMCS Firefly mission concept study. Firefly focuses on the global structure and dynamics of the Sun's interior, the generation of solar magnetic fields, the deciphering of the solar cycle, the conditions leading to the explosive activity, and the structure and dynamics of the corona as it drives the heliosphere.