标题： AD Leo中的能量粒子活动：检测到类似太阳的第四类爆发 显示英文标题

标题： Energetic particle activity in AD Leo: Detection of a solar-like type-IV burst

摘要： AD Leo是一颗年轻且活跃的M型矮星，在X射线到射电波段都有很高的耀斑率。 耀斑会加速外层日冕层中的粒子，并经常影响系外空间天气。 宽频射电动态谱使我们能够研究日冕中粒子加速活动的演变。 识别发射特征并建模机制可以提供关于驱动粒子加速过程的可能物理情景的见解。 我们使用升级版巨型米波射电望远镜（uGMRT）对AD Leo进行了550 - 850 MHz波段的8小时监测。 构建了一个名为VISAD的Python程序，以获得平均宽频动态谱。 还进行了直接成像。 基于现有的AD Leo观测结果和太阳活动区模型，得到了电子密度和磁场的径向分布。 应用这些模型，我们探讨了活动区的可能发射机制和磁场结构。 这颗恒星在整个观测过程中表现出高亮度温度（$\approx 10^{10} - 10^{11}$K），几乎100%的左旋圆偏振爆发。 耀斑后阶段以高度极化（60 - 80%）的类似太阳的IV型爆发为特征，限制在700 MHz以上。耀斑辐射倾向于Z模式或更高谐波X模式电子回旋脉泽发射机制。 700 MHz以上的耀斑后活动与由磁环中被困的耀斑加速粒子产生的IV型射电爆发一致，这可能是日冕物质抛射（CME）的特征。 这是首次在一颗年轻的活跃M型矮星上报告类似太阳的IV型爆发，其年龄相关的活动性与太阳不同。 我们还发现，活动区磁场的多极展开模型比类似太阳的活动区剖面更能解释观测到的射电辐射。 显示英文摘要

摘要： AD Leo is a young and active M dwarf with high flaring rates across the X-ray to radio bands. Flares accelerate particles in the outer coronal layers and often impact exospace weather. Wide-band radio dynamic spectra let us explore the evolution of particle acceleration activity across the corona. Identifying the emission features and modelling the mechanisms can provide insights into the possible physical scenarios driving the particle acceleration processes. We performed an 8 h monitoring of AD Leo across the 550 - 850 MHz band using upgraded-Giant Metrewave Radio Telescope (uGMRT). A python routine, named VISAD, was built to obtain the visibility averaged wide-band dynamic spectra. Direct imaging was also performed. Based on existing observational results on AD Leo and on solar active region models, radial profiles of electron density and magnetic fields were derived. Applying these models, we explore the possible emission mechanisms and magnetic field structure of the active region. The star displayed high brightness temperature ($\approx 10^{10} - 10^{11}$ K) throughout the observation with nearly 100% left circularly polarised bursts. Post flare phase is characterised by a highly polarised (60 - 80%) solar-like type IV burst confined above 700 MHz.The flare emission favors a Z-mode or a higher harmonic X-mode electron cyclotron maser emission mechanism. The post-flare activity above 700 MHz is consistent with a type-IV radio burst from flare-accelerated particles trapped in magnetic loops, which could be a coronal mass ejection (CME) signature. This is the first solar-like type-IV burst reported on a young active M dwarf belonging to a different age - related activity compared to the Sun. We also find that, a multipole expansion model of the active region magnetic field better accounts for the observed radio emission than a solar-like active region profile.