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Abstract The excess broadening of high-temperature spectral lines, long observed near the tops of flare arcades, is widely considered to result from magnetohydrodynamic turbulence. According to different theories, plasma turbulence is also believed to be a candidate mechanism for particle acceleration during solar flares. However, the degree to which this broadening is connected to the acceleration of nonthermal electrons remains largely unexplored outside of recent work, and many observations have been limited by limited spatial resolution and cadence. Using the Interface Region Imaging Spectrometer, we present spatially resolved observations of loop-top (LT) broadenings using hot (≈11 MK) Fexxi1354.1 Å line emission at ≈9 s cadence during the 2022 March 30 X1.3 flare. We find nonthermal velocities upward of 65 km s⁻¹that decay linearly with time, indicating the presence and subsequent dissipation of plasma turbulence. Moreover, the initial Fexxisignal was found to be cospatial and cotemporal with microwave emission measured by the Expanded Owens Valley Solar Array, placing a population of nonthermal electrons in the same region as the LT turbulence. Evidence of electron acceleration at this time is further supported by hard X-ray measurements from the Spectrometer/Telescope for Imaging X-rays on board Solar Orbiter. Using the decay of nonthermal broadenings as a proxy for turbulent dissipation, we found the rate of energy dissipation to be consistent with the power of nonthermal electrons deposited into the chromosphere, suggesting a possible connection between turbulence and electron acceleration. 

Aims.The aim of this work is to identify the mechanism driving pulsations in hard X-ray (HXR) and microwave emission during solar flares. Using combined HXR and microwave observations from Solar Orbiter/STIX and EOVSA, we investigate an X1.3 GOES class flare, 2022-03-30T17:21:00, which displays pulsations on timescales evolving from ∼7 s in the impulsive phase to ∼35 s later in the flare. Methods.We analysed the temporal, spatial, and spectral evolution of the HXR and microwave pulsations during the impulsive phase of the flare. We reconstructed images for individual peaks in the impulsive phase and performed spectral fitting at high cadence throughout the first phase of pulsations. Results.Our imaging analysis demonstrates that the HXR and microwave emission originates from multiple sites along the flare ribbons. The brightest sources and the location of the emission change in time. Through HXR spectral analysis, the electron spectral index is found to be anti-correlated with the HXR flux, showing a “soft-hard-soft” spectral index evolution for each pulsation. The timing of the associated filament eruption coincides with the early impulsive phase. Conclusions.Our results indicate that periodic acceleration and/or injection of electrons from multiple sites along the flare arcade is responsible for the pulsations observed in HXR and microwave emission. The evolution of pulsation timescales is likely a result of changes in the 3D magnetic field configuration over time related to the associated filament eruption. 

Abstract We present observations of a rare configuration of Mercury's magnetosphere in response to sub‐Alfvénic upstream conditions, driven by an interplanetary coronal mass ejection (ICME) that impacted the planet on 1 May 2013. Using data from the Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) spacecraft, supported by a global three‐dimensional magnetohydrodynamic (MHD) simulation of the event, we demonstrate that Mercury's magnetospheric response during this interval was distinct from the typical super‐Alfvénic state. During the sub‐Alfvénic upstream conditions, MESSENGER measured a distorted magnetotail with a depleted southern magnetotail lobe. An MHD simulation closely reproduces these observations, providing a plausible global context for the reconfiguration of Mercury's magnetosphere under sub‐Alfvénic conditions. The simulation predicts that a pair of Alfvén wings formed during this event, redirecting magnetic flux and plasma within the magnetosphere. The interplanetary magnetic field orientation during this event was primarily sunward/dawnward, generating asymmetric Alfvén wings with respect to the flow direction, in contrast to previously observed north–south wing configurations at the planet. Using Solar Orbiter observations in the inner heliosphere, we estimate that the solar wind is sub‐Alfvénic approximately 2.5 times per Earth year near solar maximum, with intervals lasting between 10 s and 12 hr. Studies of these rare, sub‐Alfvénic solar wind‐magnetospheric interactions provide valuable insights into exoplanet–stellar wind interactions under similarly sub‐Alfvénic conditions where in situ observations are not available. 

The goal of the SunPy project is to facilitate and promote the use and development of community-led, free, and open source data analysis software for solar physics based on the scientific Python environment. The project achieves this goal by developing and maintaining the sunpy core package and supporting an ecosystem of affiliated packages. This paper describes the first official stable release (version 1.0) of the core package, as well as the project organization and infrastructure. This paper concludes with a discussion of the future of the SunPy project.