arXiv subjects

Laura A. Hayes

Publications and source records attributed to Laura A. Hayes.

At least 19 recordsLinked to original sources

arXiv2026

Fine-scale flare structures and their energetic implications from short-exposure extreme-ultraviolet imaging

To capture the brightest and most rapidly evolving phases of solar flares, the Major Flare Solar Orbiter Observing Plan employed a dedicated short-exposure mode for the High Resolution Imager at 174 Angstrom (HRIEUV) of the Extreme Ultraviolet Imager. We investigate the spatial and temporal organisation of compact emission in the 19 March 2024 M2.1 flare using high-cadence, short-exposure HRIEUV observations. We combine these 0.04 s observations with hard X-ray timing, imaging, and spectroscopy from the Spectrometer Telescope for Imaging X-rays (STIX). We characterise impulsive ribbon kernels and later loop strands, and compare footpoint areas measured with HRIEUV, the Atmospheric Imaging Assembly, and STIX to constrain the local energy flux carried by flare-accelerated electrons. The short-exposure observations reveal compact emission largely obscured by saturation in normal-exposure EUV imaging. The integrated HRIEUV emission evolves co-temporally with the STIX 22-45 keV emission, with no lag discernible beyond the 2 s sampling. The ribbons comprise repeatedly activated kernels with characteristic separations of approximately 1.4-1.7 Mm, while the developing arcade shows a similar strand separation of approximately 1.3 Mm. Kernel and strand widths of approximately 0.4-0.5 Mm lie close to the instrumental resolution limit. The compact HRIEUV footpoint areas are approximately an order of magnitude smaller than those inferred from AIA or STIX, implying nominal local non-thermal energy fluxes on the order of 10^11 erg cm^-2 s^-1 at the hard X-ray peaks. These results reveal a characteristic 1-2 Mm spatial organisation of the flare emission and demonstrate the value of flare-optimised EUV imaging for future solar flare observations.

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arXiv2026

A universal scaling between damping time and period of quasi-periodic pulsations from solar EUV brightenings to X-ray stellar flares

Recent high spatial and temporal resolution extreme-ultraviolet (EUV) imaging observations have revealed that quasi-periodic pulsations (QPPs), a ubiquitous signature of impulsive energy release in solar and stellar flares, are also present in much smaller-scale coronal events known as EUV brightenings. Whether QPPs observed across such disparate spatial and energetic scales share a common physical origin remains an open question. Here we analyse 2,146 EUV brightenings observed with Solar Orbiter/EUI and 300 EUV solar flares observed with SDO/AIA, identifying 185 brightenings and 89 flares exhibiting statistically significant damped QPPs. We show that the relationship between damping time and oscillation period follows a common power-law scaling for EUV brightenings and EUV solar flares, consistent with previously reported X-ray QPPs spanning both solar and stellar flares. The persistence of this scaling over a wide range of energies and scales suggests that QPPs are governed by a common underlying physical mechanism.

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arXiv2026

Time-domain anomalies in solar and stellar flares

The temporal morphology of flare light curves encodes the underlying flare physics, and deviations from the typical flare profile may indicate the presence of mechanisms not captured by a standard flare model. To search for such time-domain deviations from a "standard" flare, we develop an unsupervised Deep Support Vector Data Description (Deep SVDD) model, which learns a compact representation of normal flares, against which unseen anomalous flares are identified. The model is trained on synthetic light curves with a "normal" flare morphology, generated from existing analytical flare trend models with noise. Using the distribution of normal flare data, we introduce a probabilistic Flare Anomaly Index (FLAI) which allows for separating flare light curves into three distinct classes: normal data (ND), weak anomalies (WA), and strong anomalies (SA). Application of FLAI to the Kepler flare catalogue (white light) reveals that 36% and 30% of events belong to the WA and SA classes, respectively. For M- and X-class solar flares from the STIX flare list, 25% and 32% of events in the 15-25 keV channel are classified as WA and SA, respectively, versus 15% for both WA and SA classes in the 4-10 keV channel. Thus, anomalous flares appear more frequently in the STIX high-energy channel. These results show that both solar and stellar flares often deviate from the normal flare population used for model training, suggesting departures from the standard flare scenario, such as modified energy release and dissipation, or the development of wave and oscillatory processes in flare sites.

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arXiv2026

Quasi-periodic pulsations and three-dimensional magnetic reconnection during 2022 March 31 flare observed by IRIS & STIX

Apparent slipping motions of flare ribbon kernels and the formation of hard X-ray (HXR) footpoints are important signatures of magnetic reconnection in solar flares. Ultraviolet (UV) and HXR ribbon emission can show quasi-periodic pulsations (QPPs), but the link between HXR QPP sources and slipping reconnection remains poorly understood. In this work, we analyze high-cadence IRIS and STIX observations of the 2022 March 31 M9.6 flare. STIX detected non-thermal QPPs with periods of $\approx$35 s from two relatively stationary footpoints. The majority of the HXR QPPs were correlated with UV pulsations observed by the IRIS Slit Jaw Imager in ribbon regions encompassing these footpoints. In one such region observed under the IRIS slit, the Si IV 1402.77Å line exhibited pulsations in intensity, Doppler shift, and width, some of which were coincident with HXR QPPs. Apparent slipping motions of the UV kernels were also observed, but their locations, timing, and UV intensity variability showed lower correlation with the HXR QPPs. The ribbons along which the slipping kernels were found correspond well to footprints of quasi-separatrix layers (QSLs), regions of high magnetic connectivity gradients, identified using a NLFFF extrapolation. Our multi-instrument analysis suggests that strong deposition of energy by non-thermal electrons was concentrated in a specific loop system within a large-scale 3D reconnection structure. Slipping kernels were subjected to weaker, if any, energization by non-thermal electrons, offering new constraints on 3D reconnection and flare energy release.

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arXiv2026

Small-Scale and Transient EUV Kernels in Solar Flare Ribbons

Flare ribbons form when energy released by coronal magnetic reconnection is deposited in the low solar atmosphere, so by studying the dynamics of flare ribbons, one obtains an indirect measurement of reconnection. Our aim is to quantify the spatial and temporal scales of substructures in the Extreme Ultraviolet (EUV) flare ribbons, known as kernels, as a probe of the spatial extent and duration of energy injection during the impulsive phase of solar flares. Unprecedented observations of an M2.5 GOES-class flare from the March 2024 major flare campaign of Solar Orbiter were used. These data were obtained at high-cadence in short-exposure mode with the Extreme Ultraviolet Imager's high-resolution telescope, HRI_EUV. Individual kernels were automatically identified using a classical computer vision algorithm. Size distributions of ribbon kernels were derived, and an average light curve of individual kernels was extracted. The EUV flare kernels were small ($\lesssim 60~\text{pixels} \approx 1~\text{Mm}^2$) and a significant fraction were unresolved at a plate scale of 135 km/pix. Furthermore, we derived surprisingly short EUV kernel heating times of less than a few seconds. The average profile exhibits a sharp rise of $1.7\pm0.3$ s from half-maximum, requiring an additional $2.3^{+0.7}_{-0.4}$ s to return to its reference value. Our findings indicate that approximately half of the kernels were unresolved in this flare, despite the enhanced angular resolution offered by Solar Orbiter's proximity to the Sun at 0.38 AU here. Furthermore, we show that energy was only injected in a localised region ($\lesssim 1~\text{Mm}^2$) of flare ribbons for less than a few seconds. These results necessitate an in-depth investigation into the implications of such small-scale and transient injections on the energy flux deposited in solar flares, and the resulting response of the solar atmosphere.

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arXiv2026

Probing the properties of active regions in the solar interface region using full-disk spectroheliograms

The composition of plasma in the solar corona is characterised by the First Ionisation Potential (FIP) bias, and is thought to be the result of a ponderomotive force acting in the chromosphere to separate ionised from neutral plasma. Identifying potential signatures of this process in the solar chromosphere is the subject of active research. Full disk spectroheliograms of the chromosphere and transition region from the Interface Region Imaging Spectrometer (IRIS) spacecraft provide an opportunity to compare plasma signatures between active regions at different evolutionary stages and assess their relationship with the fractionation processes. Here we compare the C II, Si IV, and Mg II lines observed by IRIS, finding no clear variability between active regions at different evolutionary stages in the C II and Si IV lines. However, distinct differences can be identified between the active regions using the Mg II k/h ratio (which provides a proxy for plasma opacity). In particular, the regions with the highest median FIP bias exhibit double peaked distributions of plasma opacity, suggesting variable plasma density which could affect wave propagation in these locations. These results indicate that the relationship between the plasma properties and how the plasma is fractionated should be investigated in more detail by combining observations and modelling to better understand how it changes on both temporal and spatial scales

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arXiv2025

Understanding Solar Flares and Energetic Events: Open questions, observational requirements, and instrumental needs over the coming decade

Solar flares are the largest energy-release events in the Solar System, allowing us to study fundamental physical phenomena under extreme conditions. Those include magnetic reconnection, particle acceleration, radiation transport, and various plasma physics processes, all of which occur throughout the heliosphere and rest of the Universe. Flares and eruptive events are also components of geo-effective space weather. Their impacts from a space weather perspective are numerous, such as harm to satellites, disruption to GPS, communications and power systems, and impacts on passenger air travel. A comprehensive understanding of solar flares is therefore not just a compelling science problem, but also important for national security and infrastructure. This white paper (WP) addresses critical open science questions related to solar flares. Key observations and capabilities required to make significant advancements over the coming decade are identified. The UK has a robust and vibrant solar flare community. We are key partners in international collaborations, and also provide instrumentation for existing and upcoming ESA/NASA/JAXA space missions. Continuing this effort over the coming decade is vital to maintain UK leadership in this field, achieve Solar System Advisory Panel roadmap goals, and to work under the UK Space Agency's National Space Strategy Pillars. Several complementary WPs have been submitted that discuss instruments or concepts that would directly address the observational requirements we describe (including: SPARK, solar optimised IFUs, Solar-C/EUVST, and OSIRIS), as well as required numerical modelling efforts and infrastructure.

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arXiv2025

Accessing the fine temporal scale of EUV brightenings and their quasi-periodic pulsations: 1 second cadence observations by Solar Orbiter/EUI

Small scale extreme ultraviolet (EUV) transient brightenings are observationally abundant and critically important to investigate. Determining whether they share the same physical mechanisms as larger scale flares would have significant implications for the coronal heating problem. A recent study has revealed that quasi periodic pulsations (QPPs), a common feature in both solar and stellar flares, may also be present in EUV brightenings in the quiet Sun (QS). We aim to characterise the properties of EUV brightenings and their associated QPPs in both QS and active regions (ARs) using unprecedented 1 s cadence observations from Solar Orbiter/Extreme Ultraviolet Imager (EUI). We applied an automated detection algorithm to analyse statistical properties of EUV brightenings. QPPs were identified using complementary techniques optimised for both stationary and non stationary signals, including a Fourier based method, ensemble empirical mode decomposition, and wavelet analysis. Over 500000 and 300000 brightenings were detected in ARs and QS regions, respectively. Brightenings with lifetimes shorter than 3 s were detected, demonstrating the importance of high temporal resolution. QPP periods span from 5 to over 500 s and show similar distributions between AR and QS. We found a consistent power law scaling, with a weak correlation and a large spread, between QPP period and lifetime in EUV brightenings, solar, and stellar flares. The results support the interpretation that EUV brightenings may represent a small scale manifestation of the same physical mechanisms driving larger solar and stellar flares. Furthermore, the similarity in the statistical properties of EUV brightenings and their associated QPPs between AR and QS regions suggests that the underlying generation mechanisms may not strongly depend on the large scale magnetic environment.

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arXiv2025

Systematic non-thermal velocity increase preceding soft X-ray flare onset: A large-scale Hinode/EIS study

Non-thermal velocities, derived from spectral line broadening, can provide crucial insights into plasma dynamics before and during solar flares. To systematically study the pre-flare phase, we constructed a Hinode/Extreme-ultraviolet Imaging Spectrometer (EIS) flare catalog of 1,449 flares from 2011--2024. This enabled a large-scale analysis of flare loop footpoint non-thermal velocity evolution across different flare magnitudes (C, M, X-classes). Analyzing Fe VIII--Fe XXIV emission lines formed at $\log(T/K) \sim 5.7-7.3$ with piecewise linear fits in the pre-flare period, we find that non-thermal velocities consistently increase 4--25 minutes before GOES soft X-ray start in C and M-class flares. Onset timing patterns vary with flare magnitude: smaller flares show temperature-dependent progression, while larger flares exhibit more compressed, near-simultaneous onsets across temperatures. While our limited X-class sample ($N=18$) also show onset before GOES, larger statistics are needed to confirm its behavior. M-class flares show a systematic precursor non-thermal velocity onset $\sim$30--60 minutes before GOES peak. In a subset of M-class flares (2011--2018), CME-associated events show earlier and more uniform precursor onsets (45--74 minutes before peak) than non-CME events, of which only some lines display a precursor, suggesting a strong link between extended pre-flare non-thermal broadening and successful eruptions. This large scale study establishes pre-flare non-thermal velocity increase at footpoints as a common precursor observable before any X-ray signature.

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arXiv2025

28 Years of Sun-as-a-star Extreme Ultraviolet Light Curves from SOHO EIT

The Solar and Heliospheric Observatory (SOHO) Extreme-ultraviolet Imaging Telescope (EIT) has been taking images of the Solar disk and corona in four narrow EUV bandpasses (171Å, 195Å, 284Å, and 304Å) at a minimum cadence of once per day since early 1996. The time series of fully-calibrated EIT images now spans approximately 28 years, from early 1996 to early 2024, covering solar cycles 23, 24, and the beginning of cycle 25. We convert this extensive EIT image archive into a time series of `Sun-as-a-star' light curves in EIT's four bandpasses, providing a long-term record of solar EUV variability. These Sun-as-a-star light curves, available for download from https://doi.org/10.5281/zenodo.15474179, trace the Sun as if it were a distant point source, viewed from a fixed perspective. We find that our EUV light curves trace the $\sim$ 11-year solar activity cycle and the $\sim$ 27-day rotation period much better than comparable optical observations. In particular, we can accurately recover the solar rotation period from our 284Ålight curve for 26 out of 28 calendar years of EIT observations (93% of the time), compared to only 3 out of 29 calendar years (10% of the time) of the VIRGO total solar irradiance time series, which is dominated by optical light. Our EIT light curves, in conjunction with Sun-as-a-star light curves at optical wavelengths, will be valuable to those interested in inferring the EUV/UV character of stars with long optical light curves but no intensive UV observations, as well as to those interested in long-term records of solar and space weather.

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arXiv2025

Spatiotemporal evolution of UV pulsations and their connection to 3D magnetic reconnection and particle acceleration

Quasi-periodic pulsations (QPPs) are a common feature of impulsive solar flare emissions, yet their driving mechanism(s) remain unresolved. We study long-period (3.4 min) QPPs in the M3.7 flare on Feb 24, 2023, using SDO/AIA and Solar Orbiter/STIX to pinpoint their source and driver. We analyzed UV and HXR emissions from four subregions covering the flare ribbons and footpoints of the erupting filament. We find the QPP characteristics varied significantly across these regions. The strongest UV pulsations, which correlated strongly with HXR emissions, originated from a sequence of flare kernels at the expanding front of the southern flare ribbon. In contrast, another expanding ribbon front showed no pulsations. The spatial coincidence of UV and HXR sources points to non-thermal electrons as a common driver, with the HXR spectrum showing a soft-hard-soft evolution matching the pulsation timescale. We also observed UV pulsations from plasma injections into a separate filament channel, distinct from the main flare kernels. Our results suggest that the spatiotemporal evolution of the pulsations is driven by the propagation of magnetic reconnection in an asymmetric geometry. We propose that slipping reconnection along quasi-separatrix layers is key to generating and moving the UV kernels, potentially modulated by another time-varying process.

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arXiv2025

Solar Orbiter's 2024 Major Flare Campaigns: An Overview

Solar Orbiter conducted a series of flare-optimised observing campaigns in 2024 utilising the Major Flare Solar Orbiter Observing Plan (SOOP). Dedicated observations were performed during two distinct perihelia intervals in March/April and October, during which over 22 flares were observed, ranging from B- to M-class. These campaigns leveraged high-resolution and high-cadence observations from the mission's remote-sensing suite, including the High-Resolution EUV Imager (EUI/HRI_EUV), the Spectrometer/Telescope for Imaging X-rays (STIX), the Spectral Imaging of the Coronal Environment (SPICE) spectrometer, and the High Resolution Telescope of the Polarimetric and Helioseismic Imager (PHI/HRT), as well as coordinated ground-based and Earth-orbiting observations. EUI/HRI_EUV operating in short-exposure modes, provided two-second-cadence, non-saturated EUV images, revealing structures and dynamics on scales not previously observed. Simultaneously, STIX captured hard X-ray imaging and spectroscopy of accelerated electrons, while SPICE acquired EUV slit spectroscopy to probe chromospheric and coronal responses. Together, these observations offer an unprecedented view of magnetic reconnection, energy release, particle acceleration, and plasma heating across a broad range of temperatures and spatial scales. These campaigns have generated a rich dataset that will be the subject of numerous future studies addressing Solar Orbiter's top-level science goal: "How do solar eruptions produce energetic particle radiation that fills the heliosphere?". This paper presents the scientific motivations, operational planning, and observational strategies behind the 2024 flare campaigns, along with initial insights into the observed flares. We also discuss lessons learned for optimizing future Solar Orbiter Major Flare campaigns and provide a resource for researchers aiming to utilize these unique observations.

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arXiv2025

Quasi-periodic pulsations in extreme-ultraviolet brightenings

Context. Extreme-ultraviolet (EUV) observations have revealed small-scale transient brightenings that may share common physical mechanisms with larger-scale solar flares. A notable feature of solar and stellar flares is the presence of quasi-periodic pulsations (QPPs), which are considered a common and potentially intrinsic characteristic. Aims. We investigate the properties of QPPs detected in EUV brightenings, which are considered small-scale flares, and compare their statistical properties with those observed in solar and stellar flares. Methods. We extracted integrated light curves of 22,623 EUV brightenings in two quiet Sun regions observed by the Solar Orbiter/Extreme Ultraviolet Imager and identified QPPs in their light curves using Fourier analysis. Results. Approximately 2.7 % of the EUV brightenings exhibited stationary QPPs. The QPP occurrence rate increased with the surface area, lifetime, and peak brightness of the EUV brightenings. The detected QPP periods ranged from approximately 15 to 260 seconds, which is comparable to the periods observed in solar and stellar flares. Consistent with observations of QPPs in solar and stellar flares, no correlation was found between the QPP period and peak brightness. However, unlike the trend observed in solar flares, no correlation was found between the QPP period and lifetime/length scale. Conclusions. The presence of QPPs in EUV brightenings supports the interpretation that these events may be small-scale manifestations of flares, and the absence of period scaling with loop length further suggests that standing waves may not be the primary driver of QPPs in these events.

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arXiv2025

Probing progression of heating through the lower flare atmosphere via high-cadence IRIS spectroscopy

Recent high-cadence flare campaigns by the Interface Region Imaging Spectrograph (IRIS) have offered new opportunities to study rapid processes characteristic of flare energy release, transport, and deposition. Here, we examine high-cadence chromospheric and transition region spectra acquired by IRIS during a C-class flare from 2022 September 25. Within the flare ribbon, the intensities of the Si IV 1402.77, C II 1334.53 and Mg II k 2796.35 lines peaked at different times, with the transition region Si IV typically peaking before the chromospheric Mg II line by 1 - 6 seconds. To understand the nature of these delays, we probed a grid of radiative hydrodynamic flare simulations heated by electron beams, thermal conduction-only, or Alfvén waves. Electron beam parameters were constrained by hard X-ray observations from the Gamma-ray Burst Monitor (GBM) onboard the Fermi spacecraft. Reproducing lightcurves where Si IV peaks precede those in Mg II proved to be a challenge, as only a subset of Fermi/GBM-constrained electron beam models were consistent with the observations. Lightcurves with relative timings consistent with the observations were found in simulations heated by either high-flux electron beams or by Alfvén waves, while the thermal conduction heating does not replicate the observed delays. Our analysis shows how delays between chromospheric and transition region emission pose tight constraints on flare models and properties of energy transport, highlighting the importance of obtaining very high-cadence datasets with IRIS and other observatories.

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arXiv2025

Quasi-Periodic Pulsations in Ionospheric TEC Synchronized with Solar Flare EUV Emission

The extreme ultraviolet (EUV) and X-ray radiation emitted during solar flares has been shown to significantly increase the electron density of the Earth's ionosphere. During flares, quasi-periodic pulsations (QPPs) in X-ray flux originating in the corona have previously been linked to subsequent pulsations in the Earth's ionospheric D-region. Similar pulsations have been detected in chromospheric EUV emission, although their impact on the Earth's ionosphere has not previously been investigated. Here, for the first time, synchronous pulsations were detected in solar EUV emission and ionospheric Total Electron Content (TEC) measurements. Using wavelet and periodogram analysis, we detect QPPs with approximately 85 second periods in chromospheric EUV emission lines (He II 304 Å, C III 977 Å and H I 972 Å) from the Solar Dynamics Observatory Extreme Ultraviolet Variability Experiment (SDO/EVE) during the impulsive phase of an X5.4 flare on March 7, 2012. These lines contribute to ionization in the ionospheric E- and F-regions, resulting in subsequent variations of electron density with the same periodicity, which was detected in TEC measurements. This work demonstrates that the Earth's ionosphere is responsive to fine-scale fluctuations in EUV emission during flares, with a time delay of approximately 30 seconds found. These findings may have applications in atmospheric modelling and solar-terrestrial studies, including the calculation of ionospheric recombination rates.

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arXiv2025

Bursty acceleration and 3D trajectories of electrons in a solar flare

During a solar flare, electrons are accelerated to non-thermal energies as a result of magnetic reconnection. These electrons then propagate upwards and downwards from the energy release site along magnetic field lines and produce radio and X-ray emission. On 11 November 2022, an M5.1 solar flare was observed by the Spectrometer/Telescope for Imaging X-rays (STIX) on board Solar Orbiter together with various ground- and space-based radio instruments. The flare was associated with several fine hard X-ray (HXR) structures and a complex set of metric radio bursts (type III, J, and narrowband). By studying the evolution of X-ray, extreme ultraviolet, and radio sources, we aim to study the trajectories of the flare-accelerated electrons in the lower solar atmosphere and low corona. We used observations from the STIX on board Solar Orbiter to study the evolution of X-ray sources. Using radio imaging from the Nançay Radio heliograph (NRH) and the Newkirk density model, we constructed 3D trajectories of 14 radio bursts. Imaging of the HXR fine structures shows several sources at different times. The STIX and NRH imaging shows correlated changes in the location of the HXR and radio source at the highest frequency during the most intense impulsive period. Imaging and 3D trajectories of all the bursts show that electrons are getting accelerated at different locations and along several distinct field lines. The longitude and latitude extent of the trajectories are ~30 arcsec and ~ 152 arcsec. We find that the electrons producing HXR and radio emission have similar acceleration origins. Importantly, our study supports the scenario that the flare acceleration process is temporally and spatially fragmentary, and during each of these small-scale processes, the electron beams are injected into a very fibrous environment and produce complex HXR and radio emission.

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arXiv2024

Solar flares in the Solar Orbiter era: Short-exposure EUI/FSI observations of STIX flares

Aims: This paper aims to demonstrate the importance of short-exposure extreme ultraviolet (EUV) observations of solar flares in the study of particle acceleration, heating and energy partition in flares. This work highlights the observations now available from the Extreme Ultraviolet Imager (EUI) instrument suite on board Solar Orbiter while operating in short-exposure mode. Methods: A selection of noteworthy flares observed simultaneously by the Spectrometer Telescope for Imaging X-rays (STIX) and the Full Sun Imager of EUI (EUI/FSI) are detailed. New insights are highlighted and potential avenues of investigation are demonstrated, including forward-modelling the atmospheric response to a non-thermal beam of electrons using the RADYN 1D hydrodynamic code, in order to compare the predicted and observed EUV emission. Results: The examples given in this work demonstrate that short-exposure EUI/FSI observations are providing important diagnostics during flares. A dataset of more than 9000 flares observed by STIX (from November 2022 until December 2023) with at least one short-exposure EUI/FSI 174 Å image is currently available. The observations reveal that the brightest parts of short-exposure observations consist of substructure in flaring ribbons that spatially overlap with the hard X-ray emission observed by STIX in the majority of cases. We show that these observations provide an opportunity to further constrain the electron energy flux required for flare modelling, among other potential applications.

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arXiv2024

X-ray and Spectral UV Observations of Periodic Pulsations in a Solar Flare Fan/Looptop

We present simultaneous X-ray and spectral ultraviolet (UV) observations of strikingly-coherent oscillations in emission from a coronal looptop and fan structure, during the impulsive phase of a long-duration M-class solar flare. The 50 s oscillations are observed near in-phase by Solar Orbiter/STIX, GOES, and IRIS Fe XXI intensity, Doppler and non-thermal velocity. For over 5 minutes of their approximate 35 minute duration, the oscillations are so periodic (2-sigma above the power law background), that they are better described as 'periodic pulsations' than the more-widely documented 'quasi-periodic pulsations' often observed during solar flares. By combining time-series analysis of the the multi-instrument datasets with comparison to MHD simulations, we attribute the oscillations to the magnetic tuning fork in the flare looptop-fan region, and betatron acceleration within the lower-altitude flare loops. These interpretations are possible due to the introduced 'Sliding Raster Method' (SliRM) for analysis of slit spectrometer (e.g. IRIS) raster data, to increase the temporal cadence of the observations at the expense of spatial information.

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