Title: Temperature of Solar Orbiter/EUI quiet Sun small scale brightenings: evidence for a cooler component Show Chinese title

Title: 太阳轨道器/EUI宁静日面小尺度明亮现象的温度：较冷组分的证据

Abstract: Context: On 2020 May 30, small and short-lived EUV brightenings were observed in the Quiet Sun (QS) during a four minutes sequence by EUI/HRIEUV on board Solar Orbiter. Their physical origin and possible impact on coronal or Transition Region (TR) heating are still to be determined. Aims: Our aim is to derive the statistical thermal evolution of these events in order to establish their coronal or TR origin. Methods. Our thermal analysis takes advantage of the multithermal sensitivity of the Atmospheric Imaging Assembly (AIA) imager on board the Solar Dynamics Observatory (SDO). We first identified these HRIEUV events in the six coronal bands of AIA. We then performed a statistical time lag analysis, which quantifies the delays between the light curves from different bands. These time lags can give significant insights into the temperature evolution of these events. The analysis is performed taking into account the possible contribution to the results from the background and foreground emissions. Results: The events are characterized by time lags inferior to the AIA cadence of 12 s, for all nine couples of AIA bands analyzed. Our interpretation is the possible co-presence of events which reach or do not reach coronal temperatures ($\approx$ 1MK). We believe that the cool population dominates the events analyzed in this work. Show Chinese abstract

Abstract: 上下文：2020年5月30日，通过太阳轨道器上的EUI/HRIEUV在四分钟序列中观测到了宁静太阳（QS）中的小而短暂的极紫外波段明亮现象。它们的物理起源及其对日冕或过渡区（TR）加热的可能影响仍有待确定。目标：我们的目标是推导这些事件的统计热演化，以确定它们的日冕或TR起源。方法：我们的热分析利用了太阳动力学天文台（SDO）上的大气成像组件（AIA）成像仪的多温度敏感性。我们首先在AIA的六个日冕波段中识别了这些HRIEUV事件。然后进行了统计时间延迟分析，该分析量化了不同波段光曲线之间的延迟。这些时间延迟可以为这些事件的温度演化提供重要见解。分析时考虑了背景和前景辐射对结果的可能贡献。结果：对于所有九对分析的AIA波段，这些事件的时间延迟均低于AIA的12秒采样率。我们的解释是这些事件可能同时存在达到或未达到日冕温度（$\approx$1MK）的现象。我们认为，在本研究中分析的事件中，较冷的群体占主导地位。