Coronal Elemental Abundances During A-Class Solar Flares Observed by Chandrayaan-2 XSM
Coronal Elemental Abundances During A-Class Solar Flares Observed by Chandrayaan-2 XSM
复制标题
Chandrayaan-2 XSM 观测到的 A 级太阳耀斑期间的日冕元素丰度
作者：
Lakshitha Nama;B. Mondal;S. Narendranath;K. Paul
低第一电离势（FIP）元素的丰度在闭环活动日冕中比在光球中高出三到四倍，称为FIP效应。观测表明，在不同的日冕结构中，其丰度是不同的。本文利用月船2号轨道飞行器上的太阳x射线监测器（XSM）的软x射线光谱测量结果，研究了在太阳周期24最小期观测到的多个a级耀斑的FIP效应。利用时间积分光谱分析，我们得到了平均温度、发射量和四种元素——Mg、Al、Si和s的丰度。我们发现温度和发射量与耀斑亚类有关，而测量的丰度对低a级耀斑（如A1）表现出中间的FIP偏差，而对高a级耀斑，FIP偏差接近一致。为了进一步研究它，我们对a级耀斑样本进行了时间分辨光谱分析，并检查了温度，发射测量和丰度的演变。我们发现，在耀斑的脉冲阶段，丰度从日冕值下降到它们的光球值，在脉冲阶段之后，它们迅速恢复到通常的日冕值。在耀斑的脉冲阶段，从日冕到光球的丰度值的转变表明，由于色球蒸发，新鲜的未分馏物质从太阳低层大气注入到日冕。然而，解释在耀斑衰减阶段从光球到日冕的丰度的快速恢复是具有挑战性的。
The abundances of low first ionization potential (FIP) elements are three to four times higher in the closed loop active corona than in the photosphere, known as the FIP effect. Observations suggest that the abundances vary in different coronal structures. Here, we use the soft X-ray spectroscopic measurements from the Solar X-ray Monitor (XSM) onboard the Chandrayaan-2 orbiter to study the FIP effect in multiple A-class flares observed during the minimum of Solar Cycle 24. Using time-integrated spectral analysis, we derive the average temperature, emission measure, and the abundances of four elements – Mg, Al, Si, and S. We find that the temperature and emission measure scales with the sub-class of flares while the measured abundances show an intermediate FIP bias for the lower A-flares (e.g. A1), while for the higher A-flares, the FIP bias is near unity. To investigate it further, we perform a time-resolved spectral analysis for a sample of the A-class flares and examine the evolution of temperature, emission measure, and abundances. We find that the abundances drop from the coronal values towards their photospheric values in the impulsive phase of the flares and, after the impulsive phase, they quickly return to the usual coronal values. The transition of the abundances from the coronal to photospheric values in the impulsive phase of the flares indicates the injection of fresh unfractionated material from the lower solar atmosphere to the corona due to chromospheric evaporation. However, explaining the quick recovery of the abundances from the photospheric to coronal values in the decay phase of the flare is challenging.
太阳耀斑内瞬态逆 FIP 等离子体成分演化
DOI：
10.3847/1538-4357/ab07c1
发表时间：
2019
期刊：
The Astrophysical Journal
影响因子：
--
作者：
Baker D
通讯作者：
Baker D
B 级太阳耀斑期间元素丰度的演变：使用 Chandrayaan-2 XSM 进行软 X 射线光谱测量
DOI：
10.3847/1538-4357/ac14c1
发表时间：
2021
期刊：
The Astrophysical Journal
影响因子：
--
作者：
Mondal B
通讯作者：
Mondal B