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<p>Solar flare electromagnetic radiation is frequently accompanied by quasi-periodic pulsations (QPPs), which can be observed at various wavelengths, including hard X-rays (HXRs). The investigation of QPPs provides valuable insights into particle acceleration during solar flares and dynamic processes within the solar atmosphere. This study aimed to compare the timing of QPPs with identical periods in both magnetically coupled and uncoupled HXR sources during two solar flares, SOL2014-04-18 and SOL2014-10-22, and to test the hypothesis that subminute QPPs in HXR emission are generated by intrinsic magnetic loop oscillations. To achieve these objectives, we conducted a comparative observational analysis of QPPs within eruptive and confined solar flare events (SOL2014-04-18 and SOL2014-10-22, respectively) and theoretical modeling of electron kinetics using numerical simulations. A detailed examination of the HXR source regions was performed to identify correlations between the QPPs and the magnetic field structures. The numerical modeling of accelerated electron kinetics considers various factors, such as magnetic mirroring, pitch angle scattering, betatron acceleration, inhomogeneity of plasma density distribution, and magnetic field variations. This study revealed a complex relationship between electron acceleration and the generation of QPPs. The analysis of QPP timing and synchronicity in local HXR sources for the two flares provided contrasting results. In SOL2014-04-18, the observed QPP behavior across the magnetically coupled and uncoupled regions presents challenges for simple oscillating trap models based on individual magnetic loops. Conversely, the SOL2014-10-22 event displayed more coherent QPP activity across the flare region, which is potentially indicative of a larger-scale modulation or oscillation. Numerical simulations show how magnetic field oscillations and plasma dynamics can affect electron acceleration and QPP characteristics, but highlight challenges for single oscillating loops in explaining the observed QPP amplitude evolution. Rather than fitting individual events, our simulations yield a small set of robust, falsifiable signatures of the oscillating-trap scenario, such as (i) HXR peak evolution after a single or multiple injections, (ii) pulse-width–period scaling, and (iii) specific magnetically coupled footpoints phase relations, which we compared with the observations from the two flares.</p>

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Accelerated Electron Kinetics and Hard X-ray Pulsations in Solar Flares

  • 期刊论文

  • 发表日期：

    2025年12月5日

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  • A. N. Shabalin,
  • E. P. Ovchinnikova,
  • Y. E. Charikov,
  • I. V. Zimovets

摘要

Solar flare electromagnetic radiation is frequently accompanied by quasi-periodic pulsations (QPPs), which can be observed at various wavelengths, including hard X-rays (HXRs). The investigation of QPPs provides valuable insights into particle acceleration during solar flares and dynamic processes within the solar atmosphere. This study aimed to compare the timing of QPPs with identical periods in both magnetically coupled and uncoupled HXR sources during two solar flares, SOL2014-04-18 and SOL2014-10-22, and to test the hypothesis that subminute QPPs in HXR emission are generated by intrinsic magnetic loop oscillations. To achieve these objectives, we conducted a comparative observational analysis of QPPs within eruptive and confined solar flare events (SOL2014-04-18 and SOL2014-10-22, respectively) and theoretical modeling of electron kinetics using numerical simulations. A detailed examination of the HXR source regions was performed to identify correlations between the QPPs and the magnetic field structures. The numerical modeling of accelerated electron kinetics considers various factors, such as magnetic mirroring, pitch angle scattering, betatron acceleration, inhomogeneity of plasma density distribution, and magnetic field variations. This study revealed a complex relationship between electron acceleration and the generation of QPPs. The analysis of QPP timing and synchronicity in local HXR sources for the two flares provided contrasting results. In SOL2014-04-18, the observed QPP behavior across the magnetically coupled and uncoupled regions presents challenges for simple oscillating trap models based on individual magnetic loops. Conversely, the SOL2014-10-22 event displayed more coherent QPP activity across the flare region, which is potentially indicative of a larger-scale modulation or oscillation. Numerical simulations show how magnetic field oscillations and plasma dynamics can affect electron acceleration and QPP characteristics, but highlight challenges for single oscillating loops in explaining the observed QPP amplitude evolution. Rather than fitting individual events, our simulations yield a small set of robust, falsifiable signatures of the oscillating-trap scenario, such as (i) HXR peak evolution after a single or multiple injections, (ii) pulse-width–period scaling, and (iii) specific magnetically coupled footpoints phase relations, which we compared with the observations from the two flares.